Docket Number EPA-HQ-OPP-2014-0576
www.regulations.gov

Triclopyr
Interim Registration Review Decision
Case Number 2710
December 2020
JL-
Approved by:
Mary Elissa Reaves, Ph.D.
Acting Director
Pesticide Re-evaluation Division
Date:	12-16-2020

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Table of Contents
I.	INTRODUCTION	3
A.	Updates since the Proposed Interim Registration Review Decision was Issued	4
B.	Summary of Triclopyr Registration Review	4
C.	Public Comments on the Proposed Interim Registration Review Decision and Agency
Responses	6
II.	USE AND US AGE	14
III.	SCIENTIFIC ASSESSMENTS	15
A.	Human Health Risks	15
B.	Ecological Risks	19
C.	Benefits Assessment	26
IV.	INTERIM REGISTRATION REVIEW DECISION	27
A.	Risk Mitigation and Regulatory Rationale	27
B.	Tolerance Actions	37
C.	Interim Registration Review Decision	38
D.	Data Requirements	38
V.	NEXT STEPS AND TIMELINE	39
A.	Interim Registration Review Decision	39
B.	Implementation of Mitigation Measures	39
Appendix B: Summary of Risk Mitigation for Triclopyr	42
Appendix C: Labeling Changes for Triclopyr Products	43
Appendix D: Endangered Species Assessment	50
Appendix E: Endocrine Disruptor Screening Program	51
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I. INTRODUCTION
This document is the Environmental Protection Agency's (the EPA or the Agency) Interim
Registration Review Decision (ID) for triclopyr and is being issued pursuant to 40 CFR  155.56
and  155.58. The triclopyr registration review case encompasses the following forms of the
active ingredient: triclopyr acid (acid, PC code 116001), triclopyr choline salt (COLN, PC code
116000), triclopyr butoxyethyl ester (BEE, PC code 116004), and triclopyr triethylamine salt
(TEA, PC code 116002). A registration review decision is the Agency's determination whether a
pesticide continues to meet, or does not meet, the standard for registration in the Federal
Insecticide, Fungicide, and Rodenticide Act (FIFRA). The Agency may issue, when it
determines it to be appropriate, an interim registration review decision before completing a
registration review. Among other things, the interim registration review decision may determine
that new risk mitigation measures are necessary, lay out interim risk mitigation measures,
identify data or information necessary to complete the review, and include schedules for
submitting the necessary data, conducting the new risk assessment and completing the
registration review. Additional information on triclopyr, can be found in the EPA's public docket
(EPA-HQ-OPP-2014-0576) at www.regulations.gov.
FIFRA, as amended by the Food Quality Protection Act (FQPA) of 1996, mandates the
continuous review of existing pesticides. All pesticides distributed or sold in the United States
must be registered by the EPA based on scientific data showing that they will not cause
unreasonable risks to human health or to the environment when used as directed on product
labeling. The registration review program is intended to make sure that, as the ability to assess
and reduce risk evolves and as policies and practices change, all registered pesticides continue to
meet the statutory standard of no unreasonable adverse effects. Changes in science, public
policy, and pesticide use practices will occur over time. Through the registration review
program, the Agency periodically re-evaluates pesticides to make sure that as these changes
occur, products in the marketplace can continue to be used safely. Information on this program is
provided at http://www.epa.gov/pesticide-reevaluation. In 2006, the Agency implemented the
registration review program pursuant to FIFRA  3(g) and will review each registered pesticide
every 15 years to determine whether it continues to meet the FIFRA standard for registration.
The EPA is issuing an ID for triclopyr so that it can (1) move forward with aspects of the
registration review that are complete and (2) implement interim risk mitigation (see Appendices
B and C). The Agency is currently working with the U.S. Fish and Wildlife Service and the
National Marine Fisheries Service (collectively referred to as, "the Services") to develop
methodologies for conducting national threatened and endangered (listed) species assessments
for pesticides in accordance with the Endangered Species Act (ESA)  7. Therefore, although the
EPA has not yet fully evaluated risks to federally-listed species, the Agency will complete its
listed species assessment and any necessary consultation with the Services for triclopyr prior to
completing the triclopyr registration review. Likewise, the Agency will complete endocrine
screening for triclopyr, pursuant to the Federal Food, Drug, and Cosmetic Act (FFDCA) 
408(p), before completing registration review. See Appendices D and E, respectively, for
additional information on the listed species assessment and the endocrine screening for the
triclopyr registration review.
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Triclopyr is a pyridine carboxylic acid herbicide with selective toxicity to broadleaf weeds and
some woody plants. It is classified as a group 4 herbicide according to the Weed Science Society
of America and like other herbicides in this group, its mode of action is as a synthetic auxin
(mimicking natural plant hormones). Products containing triclopyr are registered for use on rice,
orchards, rangeland and pasture, forests, rights of way, commercial turf including golf courses,
sod farms, residential/institutional turf, and aquatic sites (lakes, ponds, rivers, marshes, and
wetlands). The first pesticide products containing triclopyr were registered in 1979. The
Reregi strati on Eligibility Decision (RED) for triclopyr was published in 1998.
This document is organized in five sections: Introduction, which includes this summary and a
summary of public comments and the EPA's responses; Use and Usage, which describes how
and why triclopyr is used and summarizes data on its use; Scientific Assessments, which
summarizes the EPA's risk and benefits assessments, updates or revisions to previous risk
assessments, and provides broader context with a discussion of risk characterization; Interim
Registration Review Decision, which describes the mitigation measures necessary to address
risks of concern and the regulatory rationale for the EPA's ID; and, lastly, Next Steps and
Timeline for completion of this registration review.
A.	Updates since the Proposed Interim Registration Review Decision was Issued
In the Proposed Interim Registration Review Decision (PID) for triclopyr, EPA proposed
mitigation to prevent non-target plant damage by prohibiting triclopyr-treated materials from
being used for compost, mulch, or mushroom spawn for 30 days after application. EPA is
updating this language to focus on prohibiting these materials from being moved offsite for use
in compost or as animal feed or bedding until 30 days after application. The triclopyr PID also
proposed label language that prevented animals that had grazed on treated plant material from
being moved from the treated property until they were fed forage free of triclopyr for 3 days.
EPA is updating this language to note that animals that have grazed on treated plant material
cannot be moved to areas where manure may be collected, or sensitive crops are grown until they
are fed forage free of triclopyr for 3 days. This compost prohibition and animal clean out
language will also only be needed on products registered for applications to either turf or
pastures. These updates to the compost risk mitigation will allow for greater flexibility for
property and livestock owners while helping to prevent treated materials or manure with
triclopyr residues from entering the compost stream. In addition, minor updates to the spray drift
labeling are included in this ID. EPA has also reviewed an acute larval honey bee study (MRID
51068101), which was an outstanding data need identified in the PID, and has found the study
acceptable and the guideline satisfied.
B.	Summary of Triclopyr Registration Review
Pursuant to 40 CFR  155.50, the EPA formally initiated registration review for triclopyr with
the opening of the registration review docket for the case. The following summary highlights the
docket opening and other significant milestones that have occurred thus far during the
registration review of triclopyr.
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	December 2014 - The Triclopyr Preliminary Work Plan (PWP), the Triclopyr; Triclopyr
Triethylamine Salt (TEA); and Triclopyr Butoxyethyl Ester (BEE) Human Health
Assessment Scoping Document in Support of Registration Review, and the Registration
Review: Preliminary Problem Formulation for Environmental Fate and Ecological Risk,
Endangered Species and Drinking Water Assessments for Triclopyr were posted to the
docket for a 60-day public comment period.
	June 2015 - The Triclopyr Final Work Plan (FWP) was issued. Comments were received
from the FIFRA Endangered Species Task Force, Corteva Agriscience (formerly Dow
AgroSciences), the San Francisco Bay Regional Water Quality Control Board, and the
California Stormwater Quality Association, but comments did not alter the registration
review timeline or anticipated risk assessments. Four studies not included in the PWP
were added to the list of required studies in the FWP: field testing for pollinators
(guideline 850.3040), field trial of residues in pollen and nectar (non-guideline), aerobic
soil metabolism (guideline 835.4100), and aerobic aquatic metabolism (guideline
835.4300).
	March 2016 - A Generic Data Call-In (GDCI 116001-1546) for triclopyr was issued for
data needed to conduct the registration review risk assessments. The avian acute oral
toxicity study with passerine bird (MRID 50294201) was submitted and is in review.
	November 2019 - The Agency announced the availability of the Triclopyr, Triclopyr
Butoxyethyl Ester, and Triclopyr Salts Human Health Draft Risk Assessment to Support
Registration Review and the Triclopyr (Acid, Choline salt, TEA salt, BEE): Draft
Ecological Risk Assessment for Registration Review for a 60-day public comment period.
There were four comments from four different sources received on the risk assessments.
These comments did not change the risk assessment conclusions or registration review
timeline for triclopyr.
	September 2020 - The Agency announced the availability of the PID for triclopyr in the
docket for a 60-day public comment period, which opened on September 2, 2020 and
closed on November 2, 2020. Along with the PID, the following documents were posted
to the triclopyr docket:
o Triclopyr: Response to Comments on the Draft Risk Assessment to Support
Registration Review, dated June 9, 2020.
o Usage, Benefits and Impact Assessment for Triclopyr, dated June 11, 2020.
o Aggregate Risk Assessment for Trichloropyridinol (TCP) Metabolite of Triclopyr
(PC 116001), Chlorpyrifos (PC 059101), and Chlorpyrifos-methyl (PC 059102),
dated June 6, 2002.
	December 2020 - The Agency has completed the triclopyr ID and will post it in the
triclopyr registration review docket (EPA-HQ-OPP-2014-0576).
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C. Public Comments on the Proposed Interim Registration Review Decision and
Agency Responses
During the 60-day public comment period for the triclopyr PID, which opened on September 2,
2020 and closed on November 2, 2020, the Agency received 8 public comments. An additional
comment from the San Francisco Bay Water Quality Control Board pertaining to another case
was mistakenly posted in the triclopyr docket. Comments were received from Corteva
Agriscience, the triclopyr technical registrant, the United States Department of Agriculture
(USDA), the City of Sacramento Department of Utilities, National Agricultural Aviation
Association, the National Association of Landscape Professionals, Trugreen, and the Scotts
Company, LLC. The public comments are summarized below, along with the Agency's
responses. The Agency thanks all commenters and has considered all comments in the
development of this ID.
Comment Submitted by Corteva Agriscience (EPA-HQ-OPP-2014-0576-0056)
Comment: Corteva argued that there is insufficient evidence of compost contamination to justify
compost mitigation for triclopyr products. They stated that livestock and material holding times
will place burdens on landowners and livestock managers. Corteva proposed that EPA refrain
from requiring compost mitigation until data on triclopyr's persistence in compost is available.
Corteva also stated that the primary agricultural uses for triclopyr are for non-pollinator sites
such as rice, aquatic weeds, and non-cropland sites which presents a lower likelihood of
exposure to pollinators. Corteva also notes that other use sites such as pasture/rangeland,
forestry, and rights-of-ways may contain flowering plants but application of triclopyr will likely
cause the death of the targeted plant.
EPA Response: EPA appreciates Corteva's comment on the proposed triclopyr mitigation.
There is limited data on how long triclopyr persists in compost and there have been few reported
incidents of compost contamination involving triclopyr alone. USDA noted in its comments that
experts reported one or two cases involving homeowners that clipped turfgrass that had been
treated a day or two prior, and when green clippings were used as mulch, there was damage to
tomato plants.1 There is one incident reported of non-target plant damage from compost
involving a mixed triclopyr and clopyralid product. However, the low number of incidents does
not necessarily indicate that there is no potential for compost contamination. While there have
not been any compost contamination incidents reported associated with triclopyr alone, based on
triclopyr's fate properties, its toxicity to non-target terrestrial plants, and its structural similarity
to herbicides with known compost issues, the Agency continues to be concerned with triclopyr's
potential to contaminate compost. Due to these reasons, additional data are needed to better
understand triclopyr's potential to contaminate compost, these data are:
 A modified guideline 835.6100 terrestrial field dissipation study with a duration of at
least 30 days
1 See USDA's Ml comments at: https://www.regulations.gov/document?D=EPA-HQ-OPP-2014-0576-0059
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	A non-guideline compost kinetics study for vegetative material and manure
	A non-guideline compost bioassay study for both vegetative material and manure
For other synthetic auxin herbicides such as aminocyclopyrachlor, aminopyralid, clopyralid, and
picloram with reported compost incidents, EPA has considered a broad suite of mitigation
measures to address the concerns with compost contamination. Taking the chemical-specific
considerations into account and using a proportional mitigation approach, EPA has determined
that a statement instructing users not to use treated plant materials (e.g., hay, turf clippings) or
manure from animals that have grazed in treated areas for offsite composting or offsite animal
feed/bedding until 30 days after application is necessary. In addition, the Agency has determined
that a 3-day clean out period for livestock that have grazed on treated plant materials and are
being moved to areas where manure can be collected or where sensitive crops are grown is
necessary to address potential composting concerns for triclopyr. The updated compost
restrictions should provide more flexibility for stakeholders and add less burden for applicators,
while targeting use sites that are the most likely pathways for compost contamination. The
Agency will review the need for compost labeling in future decisions, considering any new
compost data available.
While some uses for triclopyr are on sites with little pollinator attractiveness, like rice, there is
potential exposure from pasture/rangeland, forestry, turf with blooming flowers, and rights-of-
ways uses as Corteva has noted. Corteva is correct that flowers exposed to triclopyr will likely
die eventually after application which would limit the window of time for pollinator exposure.
While EPA has not determined that mandatory pollinator specific mitigation is necessary for
triclopyr, mandatory spray drift language and non-target organism advisory statements are
necessary to mitigate potential risks to terrestrial invertebrates that may forage or live on non-
target plants near treated areas.
Given the chronic risk concerns identified to adult and larval honeybees, additional Tier II
honeybee data are needed to better assess the risks of the use of triclopyr acid. Specifically, a
Tier II semi field test for pollinators (tunnel or colony feeding) and Tier II field trial of residues
in pollen and nectar study are needed. These higher-tier data will help to refine the understanding
of potential exposure to bees from the registered uses of triclopyr, and the extent of risk at the
colony level. Data on the magnitude and persistence of triclopyr BEE in pollen and nectar is also
needed to refine the understanding of potential exposure of bees from the registered uses of
triclopyr BEE.
Comment Submitted by USDA (EPA-HQ-OPP-2014-0576-0059)
Comment: USDA noted general benefits for use of triclopyr in pasture, rangeland, forest,
orchard, non-crop settings, turfgrass, and rice. USDA stated that in pasture and rangeland,
triclopyr can be applied as a broadcast application to control larger patches of herbaceous weeds,
but these broadcast applications are limited. More broadly, triclopyr has targeted applications to
control isolated brush or trees or as basal bark or cut-stump treatments. Targeted spot treatments
have been important in orchards where applicators need to protect sensitive crops nearby. USDA
noted that compared to alternatives, triclopyr has equivalent or greater efficacy against target
weeds, provides greater safety for non-target vegetation, and offers greater flexibility with a
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wider range of application methods. Triclopyr has effectively controlled invasive trees without
injuring surrounding vegetation.
In turfgrass use sites, USDA noted that triclopyr is applied as a broadcast application as part of a
tank mix with other herbicides or alone as a targeted application to manage difficult broadleaf
weeds. USDA stated that according to its outreach to weed scientists, triclopyr has essentially
replaced clopyralid as the recommended pyridine herbicide for turfgrass for control of weeds
resistant to other herbicides. Triclopyr offered benefits for use in rice because rice is sensitive to
phenoxy herbicide alternatives (2,4-D and MCPA) and has been a critical component of an
integrated weed resistance management program. USDA argued that due to triclopyr products
being typically used for spot applications it is not valid to scale up these applications as wide-
area broadcast applications at very high rates. USDA stated that much of the risks identified in
the ecological risk assessment are driven by modeled rates of 6 and 9 lbs a.e./A.
USDA was generally supportive of proposed mitigations in the triclopyr PID that address
personal protective equipment (PPE), spray drift mitigation, environmental hazards, and
herbicide resistance management. USDA suggested that the Agency tailor the spray drift
mitigation to the specific use sites. For example, triclopyr applications to turf in residential
settings were made with equipment with nozzles that are only inches away from the top of the
turf canopy or with coarse to very coarse droplets. USDA argued that the proposed spray drift
mitigation would not be practical for products labeled for use exclusively in turfgrass. USDA
also suggested a minor editorial change for the droplet size requirement, to note that applicators
are required to select nozzles and pressure that deliver medium or coarser droplets as indicated in
manufacturers' catalogues and in accordance with ASABE S572. USDA is concerned about the
proposed compost mitigation as there are few recorded compost incidents involving triclopyr.
USDA noted that labeled uses, aside from of turfgrass and pastures, have a very small likelihood
of treated materials ending up in the compost waste stream. USDA agreed there are uncertainties
remaining on the potential for triclopyr residues to end up in compost or manure. USDA argued
that based on the data and literature available, there is evidence of low potential for persistence
in treated materials, especially when compared to other pyridine herbicides like clopyralid.
USDA cited data from various open literature studies conducted in woody plants measuring the
persistence of triclopyr in treated plant materials but notes there are no published studies on the
persistence of triclopyr residues in turfgrass. There are few studies that have looked at the
persistence of triclopyr in compost or manure. USDA found data from the Australian
government2, which studied the persistence of picloram, clopyralid, and triclopyr residues in
compost after 16 weeks of composting under commercial conditions. The study found that
triclopyr residues degraded at exponential rates compared to picloram and clopyralid.
USDA urged EPA to mitigate compost risk proportionally compared to other pyridine
herbicides. USDA suggested that EPA instead use label language that would prohibit residential
turf clippings for mulching around fruit trees or vegetables, environmental hazard language
detailing potential composting risks, and developing educational materials and best management
practices for turfgrass and pasture grass. USDA offered to facilitate the formation of a working
2 New South Wales Department of Environment and Conservation. 2004. Persistent Herbicides Risk Management
Program. Available at: https://www.epa.nsw.gov.au/resources/warrlocal/050365-herbicides.pdf
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group to resolve uncertainties regarding persistent herbicides and their impact on organic waste
products.
USD A did not think that the majority of triclopyr uses will result in exposure to pollinators as it
is either applied to non-pollinator attractive crops or applied to the basal bark or stump. They
contended that pasture and rangeland are the most realistic uses that could expose pollinators to
triclopyr and suggests that the environmental hazard language for pollinators could be applied to
just these uses. USDA suggested that EPA work closely with the registrant to ensure that the Tier
II testing is designed to likely capture realistic exposure scenarios based on triclopyr use sites
likely to be attractive to pollinators.
EPA Response: The Agency appreciates the information provided by USDA concerning the
benefits of triclopyr as well as additional stakeholder feedback on the compost issue. EPA
acknowledges that there is not enough information on the persistence of triclopyr residues in
turfgrass. EPA's review of the open literature indicates that triclopyr residues were observed in
plant materials that may be used for mulch and/or composting.3'4 The level of triclopyr residues
found, following application, depends on factors such as application rate, the type of plant
foliage, and environmental factors. The persistence of triclopyr residues in plant tissues appears
to be dependent on the type of plant.5 And in animals feeding on triclopyr-contaminated feed,
triclopyr was excreted mainly in urine and not in feces.6 EPA did a cursory review of the
Australian government study cited by USDA, and while the study does show that triclopyr
degrades quickly compared to picloram and clopyralid, residues in compost would still be a
concern because even after 6 weeks, there was still about a third of triclopyr's initial
concentration remaining.
In its comments, USDA noted the lack of compost incidents for triclopyr, but noted later in its
comments that "experts did report one or two cases involving homeowners that clipped turfgrass
that had been treated a day or two prior... and when the green clippings were used as a green
mulch on tomatoes, the turf clippings resulted in damage to the tomato plant." These incidents
were not reported to EPA, and this is the first that the Agency has received news of any compost
incidents associated with triclopyr-treated residential grass clippings. However, this confirms
EPA's concerns that users may not know how to report incidents to the Agency, and even when
incidents are reported, the source of phytotoxicity is difficult to determine without residue
testing, which can be expensive. The low frequency of reported compost incidents is not
evidence that compost contamination is not of concern for triclopyr.
Newton M. et al 1990. Deposition and Dissipation of Three Herbicides in Foliage, Litter, and Soil of Brush fields
of Southwest Oregon. J. Agric. Food Chem. 1990, 38, 574-583. Available at:
https://pubs.acs.org/doi/pdf/10.1021/if00Q92a052
4	Wenxi Li. et al 2018. Residue determination of triclopyr and aminopyralid in pastures and soil by
gas chromatography-electron capture detector: Dissipation pattern under open field conditions. Ecotoxicity and
environmental safety volume 155, 15 My 2018, Pages 17-25
Available at: https://www.sciencedirect.eom/science/article/abs/pii/S0.l.476513183012107via%3Dihnb
5	Norris, L. et al 1987. Triclopyr Persistence in Western Oregon Hill Pastures. Environmental Bulletin of
Environmental Toxicology (1987) 39:134-141. Available at: https://link.springer.com/article/10.1007/BF01691801
6	Eckerlin, R.H et al 1987. Excretion of triclopyr herbicide in the bovine. Bulletin of Environmental Toxicology
(1987) 39:443-447. Available at: https://link.springer.com/article/10.1007/BF016883Q8
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For other synthetic auxin herbicides such as aminocyclopyrachlor, aminopyralid, clopyralid, and
picloram with reported compost incidents, EPA has considered a broad suite of mitigation
measures to address the concerns with compost contamination. The Agency is requiring
compost labeling for persistent herbicides based on a weight of evidence approach. Based on
triclopyr's fate properties, its toxicity to non-target terrestrial plants, its structural similarity to
herbicides with known compost issues, and information from comments submitted by USDA
noting a couple compost incidents associated with residential turf clippings, the Agency
continues to be concerned with triclopyr's potential to contaminate compost. Taking the
chemical-specific considerations into account and to continue to use a proportional mitigation
approach, as USDA suggested, EPA is updating the compost prohibition to focus on preventing
offsite transportation of treated plant materials and manure for composting and animal
feed/bedding uses for 30 days after application. The Agency is also changing the animal clean
out period language to clarify that animals should not be moved to areas where manure can be
collected or where sensitive crops are grown until they have been fed forage free of triclopyr for
3 days. The compost mitigation language will also only be required on products with pasture and
turf use sites, since these sites are thought to have the highest risks for materials entering the
compost stream. These updates to the compost restrictions should provide more flexibility for
stakeholders and add less burden for applicators, while targeting use sites that are the most likely
pathways for compost contamination.
In the triclopyr PID, the spray drift labeling within the document was not consistent between
Section IV of the document and the label table. In this ID, EPA has corrected those differences
as USDA suggested, and is also making changes to the references to the AS ABE standard for
aerial application equipment. While USDA suggested altering the spray drift requirements based
on certain application sites, such as turfgrass, EPA's spray drift labeling is associated with
certain application equipment (i.e., ground boom and aerial application equipment) and not a
particular use site. No exceptions for certain crops or uses have been added in this ID.
As described in EPA's response to the Corteva pollinator comments above, mandatory spray
drift language and non-target organism advisory statements are necessary to mitigate potential
risks to terrestrial invertebrates that may forage or live on non-target plants near treated areas.
Given the chronic risk concerns identified to adult and larval honeybees, additional Tier II
honeybee data are needed for triclopyr acid.
USDA stated applications of triclopyr are often spot treatments and the high rates, up to 6 to 9
lbs ae/A, included in EPA's ecological risk assessment may not reflect the actual use of these
products. EPA's ecological risk assessment calculated potential triclopyr risk using the
maximum allowed rates on triclopyr labels. However, the triclopyr PID also included additional
information provided by USDA on more typical triclopyr use rates, leading EPA to conclude that
risks to non-target organisms from use on forests, non-crop areas, and rights of ways are likely
lower than estimated in the ecological risk assessment.
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Comment Submitted by Sacramento River Source Water Protection Program (SRSWPP)
(EPA-HQ-OPP-2014-0576-0054)
Comment: SRSWPP expressed concern regarding the potential for triclopyr, and its metabolite
trichloropyridinol (TCP), to affect drinking water quality. There was concern that surface water
modeling in the Agency's drinking water assessment fails to incorporate estimates of exposure
from the metabolite TCP. SRSWPP also argued that the 2002 TCP aggregate risk assessment
uses methods and assumptions that are outdated and should not be relied upon for assessment of
drinking water exposure from triclopyr and TCP. Although Estimated Drinking Water
Concentrations (EDWCs) were calculated, there is remaining concern as these values were not
compared to environmental reference values, such as Human Health Benchmarks for Pesticides
(HHBPs). For surface water, the chronic EDWC produced by EPA's modeling exceeds EPA's
chronic HHBP. SRSWPP cited water monitoring data to support their concern regarding
exposure to TCP via drinking water consumption. SRSWPP noted that the proposed spray drift
mitigation may help to reduce potential surface water contamination via drift, but additional
mitigation may be needed to reduce triclopyr transport into water supplies. They suggest that the
surface water advisory for agricultural products be replaced by a mandatory requirement for
vegetative buffer strips between agricultural land where triclopyr is applied and surface water,
that products should not be applied within 48 hours of expected rainfall or irrigation, and that
labels specify that products should not cause triclopyr concentrations to exceed a chronic HHBP
of 300 ppb. SRSWPP also asked that EPA evaluate effects of the metabolites, degradates, and
transformation products formed during and subsequent to the water treatment process, assess
cumulative effects of pesticides and their breakdown products in drinking water, and require
water quality monitoring and data collection by registrants to support these evaluations.
EPA Response: The Agency thanks SRSWPP for their comment on the triclopyr PID. HHBPs
are screening-level values for informational use by public utilities, and the approach for deriving
HHBPs differ from EPA's methodology for assessing pesticidal exposures and risks under the
FIFRA and the FFDCA. The HHBP is used to determine a level of pesticide concentration that
may indicate a potential health risk assuming a default relative drinking water source
contribution of 20 percent and are not legally-enforceable standards. As noted in the triclopyr
human health risk assessment, the dietary (food and water) and aggregate exposures are well
below the level of concern.
Regarding potential cumulative effects, EPA has not made a common mechanism of toxicity
finding as to triclopyr and any other substances, but has noted that an environmental degradate of
triclopyr, TCP, may also be an environmental degradate of other registered pesticides. While
TCP is derived from multiple chemicals, the conclusions of the 2002 TCP risk assessment
demonstrate that the aggregate dietary exposure to TCP is not a risk of concern, as the total usage
for all the compounds (that generate TCP) is lower now than 2002. NHANES biomonitoring
studies show that levels of the metabolite TCP has reduced considerably from 2000-2010, further
indicating that there is less exposure to TCP.7 For the purposes of this action, therefore, EPA has
not assumed that triclopyr has a common mechanism of toxicity with other substances. Given
7 https://www.cdc.gov/nchs/nhanes/index.htm
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that no dietary or aggregate risks of concern were identified for triclopyr, the Agency determined
that no additional mitigation is necessary to address drinking water exposures.
Comment Submitted by National Agricultural Aviation Association (NAAA) (EPA-HQ-
OPP-2014-0576-0055)
Comment: NAAA stated the overall importance of aerial applications and the advantages of
aerial applications over other forms of application. While NAAA supports the proposed spray
drift mitigation language for aerial applications, NAAA described the need for clear label
language regarding the specific altitude above which temperature inversions are not of concern.
NAAA states it is currently collaborating with the USDA-ARS Aerial Application Technology
Research Unit to conduct a literature review on the matter.
NAAA does not find the PF-10 respirator requirement for mixing and loading for aerial forestry
use to be overly burdensome but is concerned that the estimated risks that lead to this
requirement may be based largely on the greater number of acres treated daily by aerial
application compared to the other application methods. NAAA argues that if PPE is used
properly, mixing and loading for more acres should not automatically be assumed to increase the
exposure to a mixer/loader.
EPA Response: EPA thanks NAAA for the comments and for its work with USDA-ARS to
conduct a literature review. The Agency will review any additional information submitted
regarding the altitude of temperature inversions as it relates to pesticide applications. The
Agency will also consider revisions to the label language if supported by the information
submitted.
EPA's occupational risk assessment does consider the number of acres typically treated in a day
in the calculation of occupational handler risk. This assumes the longer someone is doing a
particular task, the more potential exposure they may receive in a given time period. While PPE,
like respirators, do help reduce exposure, they do not eliminate it completely. Aerial forestry
applications were assessed using a lower acreage assumption of 1,200 (where the default is 7,500
acres). At this lower acreage assumption, risks of concern for mixers/loaders for aerial forestry
applications were still identified due to the use of a 10X database uncertainty factor for lack of a
guideline 870.3465 subchronic inhalation toxicity study. At the request of the registrant, Corteva
Agriscience, EPA agreed to waive the requirement for the subchronic inhalation toxicity study if
a respirator was added to labels for mixers/loaders for the aerial forestry scenario.
Comment Submitted by National Association of Landscape Professionals (NALP) (EPA-
HQ-OPP-2014-0576-0053)
Comment: The National Association of Landscape Professionals state the importance of
triclopyr to the lawn care and landscaping business. NALP states that turf uses of triclopyr are
unlikely to result in exposure to pollinators since the application of triclopyr to turf is intended to
keep blooming weeds from proliferating. NALP also notes that there have been no compost
contamination incidents for triclopyr products and that professional landscapers do not use grass
clippings as mulch. Due to EPA's concerns for pollinators and compost contamination, NALP
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sees the need for the development and adoption of best management practices for triclopyr use
(or even pyridines generally) in lawn and landscape settings to educate applicators on these
issues.
EPA Response: EPA thanks NALP for their comments on the triclopyr PID. Similar comments
related to pollinators were received from Corteva and EPA's response is provided above. While
EPA is not requiring a registrant-generated stewardship plan for triclopyr, the Agency agrees that
the education of applicators and land managers on turf best management practices for the
pyridine herbicides as a group is important. Education and stewardship efforts are being initiated
for other pyridine herbicides with compost contamination concerns. As additional education or
stewardship materials related to compost concerns are made available, EPA will continue to
encourage the distribution of those resources to other stakeholders.
Comment Submitted by Trugreen (EPA-HQ-OPP-2014-0576-0057)
Comment: Trugreen stresses the importance of triclopyr to the lawn and landscape industries.
Trugreen is concerned about the proposed compost mitigation and does not believe that compost
mitigation is warranted for triclopyr until EPA has fully considered all available science,
investigated any incident claims, and evaluated impacts of the mitigation. Trugreen states that
while triclopyr may be present in plant material for 30 days after application, its persistence in
plant tissue alone cannot determine the impact on treated grass clippings used as compost. It is
more important to understand how triclopyr can release from clippings and be absorbed by non-
target plants at concentrations high enough to produce phytotoxicity. Trugreen also noted it was
not aware of any compost related incidents in its 30-year history of using triclopyr.
EPA Response: EPA thanks Trugreen for the comments on the triclopyr PID. As mentioned in
responses to similar compost mitigation comments from USDA and the registrant, Corteva, the
lack of incidents is not evidence that incidents are not occurring. Compost incidents may not be
reported, and even when reported, it is difficult to verify the source of phytotoxicity without
laboratory testing, which can be expensive. The Agency agrees it is important to understand
how triclopyr can release from grass clipping and be absorbed by non-target plants, which is why
additional compost studies are being required for triclopyr. Until adequate compost data are
available, EPA is using a weight of evidence approach to determine if compost labeling is
needed for certain persistent herbicides. Based on its fate properties, its toxicity to non-target
plants, and its structural similarity to pesticides with known compost issues, EPA continues to
have concerns with potential compost contamination for certain triclopyr uses, such as pasture
and residential turf. The Agency has determined that label statements noting that treated plant
materials and manure from animals that have grazed on treated sites should not be transported
offsite for recycling into compost for 30 days after application are necessary to help inform land
managers of the potential for down-stream phytotoxicity. The Agency has also determined that a
3-day grazing animal clean-out period is necessary for triclopyr.
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Comment Submitted by the Scotts Company, LLC (EPA-HQ-OPP-2014-0576-0051)
Comment: The Scotts Company sought clarification on the necessary labeling for residential
consumer products. They also suggested that, for consumer products, if the registrant reviews the
Label Review Manual and determines that gloves are applicable, then "waterproof gloves"
should be added. The Scott's Company noted that the mode of action and other resistance
management information is not applicable to residential consumer products.
EPA Response: The Agency agrees with the Scotts Company that mode of action information
and other resistance management labeling is not necessary for residential consumer products.
The Agency appreciates the information provided and has added clarification to the Appendix B
label table. The appropriate glove material is dependent on the individual product formulation
and the acute dermal exposure toxicity profile of each individual formulation. EPA is not
changing the updated glove statement language as waterproof gloves may not be appropriate for
every product and urges each registrant to choose the appropriate glove type(s) to list on their
label based on the current guidance in the Label Review Manual.
II. USE AND USAGE
Triclopyr is a group 4 systemic herbicide according to the Weed Science Society of America's
site of action group number. It acts as a synthetic auxin and causes uncontrolled cell division
and growth resulting in vascular tissue destruction at low concentrations and inhibits cell
division and growth at higher concentrations. It is in the pyridine carboxylic acid family and is
used to control broadleaf weed species and woody plants and vines postemergence in agricultural
use sites in rice, citrus in Florida, orchards in California, pasture and rangeland, and non-
agricultural use sites including forestry, rights of ways, sod farms, commercial/institutional turf,
and residential lawns. It is also used to control aquatic weeds growing in lakes, ponds, reservoirs,
and wetlands, and to control woody brush and herbaceous weeds in wetlands and on the banks
and shores of aquatic sites.
Triclopyr products are formulated as soluble concentrates, emulsifiable concentrates, liquids,
granules, wettable powders, and pellets. For granular formulations, granules are broadcasted onto
turf in wet conditions and onto aquatic weeds present on the water surface and those present in
the subsurface. For liquid formulations and water dispersible granules, a tank mix is prepared
with an agriculturally labeled non-ionic surfactant and/or other herbicide, and the liquid is
sprayed onto the target plants or aquatic weeds. Triclopyr can be applied as a broadcast
application, or as a non-broadcast application such as cut stump and basal bark treatments, hack
and squirt treatment, and girdle treatment. The broadcast applications may be applied using
ground (backpack or truck-mounted pressure sprayers) or aerial equipment. Broadcast
applications are used for control of weeds (terrestrial and aquatic) and woody plants in registered
use sites by uniform spray targeting plant foliage. Ground equipment is typically used for
spraying individual brush plants, woody plants and vines or spot treatment of weeds. The non-
broadcast methods listed above are used to target undesirable woody plants in highly localized
treatments.
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The primary agricultural use sites for triclopyr are pastureland and rice. Approximately 1.1
million pounds of triclopyr are applied to 2.3 million acres per year, according to agricultural
usage data. Pasture and rangeland accounts for approximately 1 million pounds applied on 1.8
million acres, which is an estimated 90% of all pounds of triclopyr applied annually and 80% of
all acres treated with triclopyr annually. The second largest agricultural use site is rice, which
accounts for about 10% of all pounds of triclopyr applied annually and 20% of all acres treated
with triclopyr annually. Rice has the highest percent crop treated (PCT), at approximately 15%.
For non-agricultural uses, triclopyr is applied in industrial vegetation management,
recreational/commercial/industrial turf, golf courses, landscape ornamentals, ornamental
nurseries and residential lawns. In 2016, 3.1 million pounds of triclopyr were applied in
industrial vegetation management sites and over 40,000 pounds of triclopyr were applied to
residential lawns by professional lawn care operators. In 2013, approximately 1.8 million pounds
of triclopyr were applied on professional lawn and ornamental sites.
For additional information on the usage of triclopyr, see the document Usage, Benefits and
Alternatives for Triclopyr.
III. SCIENTIFIC ASSESSMENTS
A. Human Health Risks
A summary of the Agency's human health risk assessment is presented below. The Agency used
the most current science policies and risk assessment methodologies to prepare a risk assessment
in support of the registration review of triclopyr. For additional details on the human health
assessment for triclopyr, see the Triclopyr, Triclopyr Butoxyethyl Ester, and Triclopyr Salts.
Human Health Draft Risk Assessment to Support Registration Review, which is available in the
public docket.
1. Risk Summary and Characterization
Dietary (Food + Water) Risks
The Agency's dietary (food + water) risk assessment did not identify risks of concern. Acute
dietary risk estimates were calculated but found not to be a concern; the highest exposed
population subgroup is females between 13 to 49 years with risk estimates equal to 92% of the
acute population-adjusted dose (aPAD), where risk estimates greater than 100% are of concern.
Chronic dietary risk estimates were calculated but found to not be of concern. Children <1 years
old were the highest-exposed population subgroup, with risk estimates equal to 46% of the
chronic population-adjusted dose (cPAD), the Agency's level of concern for dietary risk is 100%
of the PAD. Therefore, there are no dietary risks of concern for triclopyr.
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Residential Handler Risks
A residential handler dermal assessment was not conducted due to the lack of a dermal toxicity
endpoint. Short-term inhalation exposures were assessed. The results of the residential handler
exposure and risk assessment indicate that short-term inhalation risks are not of concern for all
turf scenarios with margins of exposure (MOEs) ranging from 4,000 to 120,000 (where MOEs
below the level of concern [LOC] of 1,000 are of concern).
Residential Post-Application Risks
A residential post-application dermal assessment was not conducted due to the lack of a dermal
toxicity endpoint. Short-term oral and inhalation exposures were assessed. Short-term incidental
oral post-application risk estimates for all turf scenarios are not of concern (i.e., MOEs > 100)
with MOEs ranging from 220 to 98,000 (where MOEs below the LOC of 100 are of concern).
Because triclopyr is applied directly to water for aquatic weed treatment, the Agency assessed
post-application risks from swimming. Short-term inhalation post-application risk estimates for
all swimmer scenarios are not of concern with MOEs ranging from 520,000 and 4,400,000 for
children 3 to <6 years old and adults, respectively (where MOEs below the LOC of 1,000 are of
concern). The post-application ingestion risk estimates for swimmers are also not of concern
with MOEs ranging from 45,000 to 580,000 for children 3 to <6 years old and adults,
respectively (where the LOC is 100).
Aggregate Risks
Aggregate risks reflect combined dietary (food and drinking water) and residential exposures.
All aggregate risk estimates for triclopyr are not of concern.
Non-occupational Spray Drift
Non-occupational spray drift risk estimates reflect exposures for children and adults who have
contact with turf where residues are assumed to be deposited via spray drift. A quantitative spray
drift assessment for triclopyr was not required because the maximum application rate to a
crop/target site multiplied by the adjustment factor for drift is less than the maximum direct
spray residential turf application rate for any triclopyr products. Turf residential post-application
MOEs are considered protective of this scenario. Since there are no residential post-application
risks of concern for turf, there are no non-occupational spray drift risks of concern.
Cumulative Risks
The EPA has not made a common mechanism of toxicity to humans finding as to triclopyr and
any other substance. A 2002 risk assessment of trichloropyridinol (TCP), a metabolite derived
from multiple chemicals including triclopyr, was conducted and the Agency found that the acute
and chronic dietary aggregate exposure estimates are below the LOC and are not a risk of
concern. Since the conclusions of the 2002 TCP assessment are still considered valid, the EPA
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has not assumed that triclopyr has a common mechanism of toxicity with other substances for the
registration review risk assessment.
Occupational Handler Risks
Occupational handlers are individuals who are involved in the pesticide application process
(including mixers, loaders, and applicators). All handlers are assumed to wear baseline attire,
which consists of long-sleeved shirt, long pants, and shoes plus socks. For most occupational
handler scenarios, inhalation MOEs ranged from 1,200 to 180,000 and were not of concern
(where MOEs below the LOC of 1,000 are of concern) with baseline clothing (no respiratory
protection) for both the short- and intermediate-term exposure durations. For aerial forestry
applications, the baseline MOE for mixer/loaders is 250 and is therefore a potential risk of
concern (LOC= 1,000). With the addition of a protection factor 10 (PF-10) respirator, the MOE
would be 2,500 which is not of concern.
A dermal endpoint was not selected; therefore, a quantitative dermal assessment was not
conducted for occupational handler exposures.
Occupational Post-Application Risks
Post-application exposure describes exposures that occur when individuals are present in an
environment that has been previously treated with triclopyr and includes activities such as
hand-weeding or hand-harvesting. A dermal endpoint was not selected; therefore, a quantitative
occupational post-application dermal assessment was not conducted.
A quantitative occupational post-application inhalation exposure assessment was not performed.
Occupational handler inhalation exposure is likely to result in higher exposure than occupational
post application inhalation exposure. Since occupational inhalation handler exposure is not of
concern, it is expected that occupational post-application inhalation exposure is also not a risk of
concern. Product specific restricted entry intervals (REIs) for uses under the Worker Protection
Standard should be based on the appropriate technical and product-specific acute toxicity
categories as described in the EPA's Label Review Manual8.
2. Human Incidents and Epidemiology
The last triclopyr human incidents search was conducted in 2014. The 2014 search found 928
incidents involving triclopyr, but the vast majority of incidents were of low severity. An updated
search for human incidents was conducted on June 19, 2019 for new incidents since the 2014
search. Both the Incident Data System (IDS) and NIOSH Sentinel Event Notification System for
Occupational Risk (SENSOR)-Pesticides databases were searched.
From January 1, 2014 to June 19, 2019, there were 47 triclopyr incidents involving a single
active ingredient and 47 triclopyr incidents involving multiple active ingredients were reported to
Main IDS and there were 600 triclopyr incidents reported to Aggregate IDS. The number of
8 https://www.epa.gov/pesticide-registration/label-review-manual
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incidents reported to IDS has declined by 59% over the last 10 years, from 222 incidents
reported in 2009 to 92 incidents reported in 2018.
A query of SENSOR-Pesticides identified 74 cases involving triclopyr from 2011 to 2015, 15 of
which involved a single active ingredient. A review of incidents in both IDS and SENSOR-
Pesticides indicates that most incidents usually were of minor severity. Based on the decline in
incidents reported to IDS and the decline in triclopyr incidents reported to both IDS and
SENSOR-Pesticides, there does not appear to be a concern at this time.
The Agricultural Health Study (AHS) is a federally-funded study that evaluates associations
between pesticide exposures and cancer and other health outcomes and represents a collaborative
effort between the US National Cancer Institute (NCI), National Institute of Environmental
Health Sciences (NIEHS), Centers for Disease Control and Prevention's (CDC's) National
Institute of Occupational Safety and Health (NIOSH), and the US EPA. Triclopyr is included in
the AHS and two studies investigated triclopyr exposure and any association with wheeze and
sleep apnea. There is insufficient epidemiological evidence at this time to conclude that a clear
associative or causal relationship exists between triclopyr and the health outcomes of wheeze and
sleep apnea assessed in the two AHS studies reported.
The Agency will continue to monitor the incident information. Additional analyses will be
conducted if ongoing human incident monitoring indicates a concern.
3. Tolerances
Tolerances for triclopyr are established under 40 CFR 180.417. A number of tolerances need to
be modified for consistency with current Organization for Economic Cooperation and
Development (OECD) rounding practices and commodity definitions. The anticipated changes to
the tolerances for triclopyr are noted in Table 1. The Agency intends to undertake these tolerance
actions pursuant to its Federal Food, Drug Cosmetic Act (FFDCA) authority.
Table 1: Summary of Anticipated Tolerance Actions for Triclopyr
Commodity/
Correct Commodity Definition
Established Tolerance
(ppm)
Anticipated
Tolerance (ppm)
Comments
180.417(a)(1)
Egg
0.05
0.05

Fish, shellfish, crustacean

3.5
Commodity definition revision.
Corrected values to be consistent
with OECD Rounding Class
Practice.
Fish, freshwater, finfish

3
Fish
3.0

Fish, shellfish, mollusc

3.5
Shellfish
3.5

Grass, forage, fodder and hay,
group 17, forage
--
700
Grass, forage
700.0

Grass, forage, fodder and hay,
group 17, hay

200
Grass, hay
200.0

Milk
0.01
0.01

Poultry, fat
0.1
0.1
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Commodity/
Correct Commodity Definition
Established Tolerance
(ppm)
Anticipated
Tolerance (ppm)
Comments
Poultry, meat
0.1
0.1

Poultry, meat byproducts, except
kidney
0.1
0.1
Rice, grain
0.3
0.3
180.417(a)(2)
Cattle, fat
0.10
0.1
Corrected values to be consistent
with OECD Rounding Class
Practice.
Cattle, meat
0.10
0.1
Cattle, meat byproducts,
0.50
0.5
Goat, fat
0.10
0.1
Goat, meat
0.10
0.1
Goat, meat byproducts
0.50
0.5
Hog, fat
0.10
0.1
Hog, meat
0.10
0.1
Hog, meat byproducts
0.50
0.5
Horse, fat
0.10
0.1
Horse, meat
0.10
0.1
Horse, meat byproducts
0.50
0.5
Sheep, fat
0.10
0.1
Sheep, meat
0.10
0.1
Sheep, meat byproducts
0.50
0.5
4. Human Health Data Needs
A guideline 870.3465 90-day inhalation toxicity study was required as part of the triclopyr
registration review GDCI (GDCI-116001-1546). Although this study has not been submitted, in
conversations with the Agency (May 6, 2020), Corteva Agriscience, the technical registrant,
notes that it intends to add a respirator on labels to protect mixers/loaders for aerial forestry
application. When this change is applied on labels during registration review labeling
implementation, the Agency will consider waiving the 90-day inhalation toxicity data
requirement. A guideline 875.2100 chemical specific turf transferable residue (TTR) study was
noted as a data gap in the scoping document and human health risk assessment. This TTR study
has been submitted (MRID 45249601) and has been reviewed. The TTR study does not impact
the current risk conclusions because the residential exposures are similar or lower than what was
assessed in the human health risk assessment. In 2016, the Agency reevaluated the toxicological
endpoints and determined no hazard was identified for the dermal exposure and therefore a
quantitative dermal assessment is not needed. No additional human health data are required to
support triclopyr registration review at this time.
B. Ecological Risks
A summary of the Agency's ecological risk assessment is presented below. The Agency used the
most current science policies and risk assessment methodologies to prepare a risk assessment in
support of the registration review of triclopyr. For additional details on the ecological assessment
for triclopyr, see the Triclopyr (Acid, Choline salt, TEA salt, BEE): Draft Ecological Risk
Assessment for Registration Review, which is available in the public docket.
The EPA is currently working with its federal partners and other stakeholders to implement an
interim approach for assessing potential risk to listed species and their designated critical
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habitats. Once the scientific methods necessary to complete risk assessments for listed species
and their designated critical habitats are finalized, the Agency will complete its endangered
species assessment for triclopyr. See Appendix D for more details. As such, potential risks for
non-listed species only are described below.
1. Risk Summary
The following forms of triclopyr were assessed: triclopyr acid, triclopyr butoxyethyl ester
(BEE), triclopyr choline (COLN), and triclopyr triethylamine salt (TEA). Triclopyr has a broad
range of use sites, and application parameters vary depending on the use site. Table 2 details the
application parameters assessed for each use site category in the 2019 ecological risk assessment.
Table 2. Application parameters assessed by use site
Use site
Maximum single
application rate
Number of
applications
Retreatment interval
Rice
0.375 lb ae/A
2
20 days
Turf
1 lb ae/A
4
28 days
Forestry
6 lb ae/A
1
Not specified on
labels
Non-crop areas, rights
of ways
9 lb ae/A
1
Not specified on
labels
Pasture, rangeland
9 lb ae/A for spot
treatment (labels
specify 2 lb ae/A for
wide area broadcast
treatment)
1
Not specified on
labels
Aquatic weed control
Calculated
by equation
present on
the label, highest
application is 5,000
ppb
1
Not specified on
labels
Tree cut stump
6 lb ae/A
1
Not specified on
treatment


labels
The Agency originally assessed pasture and rangeland uses at a maximum rate of 9 lb ae/A in its
2019 risk assessment as some labels note this maximum rate for spot treatment of grazable land
that intersects with non-crop areas and for individual plant treatment on grazable lands.
However, the maximum labeled seasonal rate for wide area broadcast treatment of pasture and
rangeland is 2 lb ae/A as noted on current labels. Pasture and rangeland are perennial cropping
systems, so the maximum seasonal rate for wide area broadcast treatment is equivalent to the
maximum yearly rate. As individual plant treatments on grazable lands and spot treatments, at a
maximum rate of 9 lb ae/A, for grazable lands that intersect with non-crop areas are
geographically limited, risk estimates for wide area broadcast application to pasture and
rangeland at 2 lb ae/A is expected to more accurately reflect risk to non-target organism from
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pasture/rangeland use on a broader scale. Revised risk estimates for pasture and rangeland are
detailed in the Triclopyr: Response to Comments on the Draft Risk Assessment to Support
Registration Review, also located in the public docket.
Many of the high risk quotients (RQs) from triclopyr use are associated with the high maximum
application rates ranging from 6 to 9 lb ae/A for uses in forestry, non-cropland areas, tree cut
stump treatment, and rights of ways. Applications at these high rates are generally rare and when
used, applications are highly localized and are done as brush treatment, basal bark treatment,
stump treatment, hack and squirt treatment, frill or girdle treatment, and as spot treatment for
targeted management of undesirable trees, shrubs, or other vegetation. Triclopyr can be applied
via aerial applications in forestry settings but aerial applications are geographically limited and
typically applied at a lower rate than the 6 lb ae/A rate assessed in risk assessment.9 Information
gathered by USDA's Office of Pest Management Policy from the US Forest Service suggest that
application of triclopyr in public forests occur at applications between 1-2 lb ai/A. Private
foresters reported primarily using rates between 1-2.5 lb ai/A. An application rate of 1-2 lb ai/A
is more common when applying triclopyr as a broadcast foliar treatment, aerial or ground, for the
control of undesirable vegetation across forestry, non-cropland areas, and rights of ways use
sites.10 The Agency concludes that risk to non-target organisms from use on forests, non-crop
areas, and rights of ways is likely lower than estimated and is likely to be geographically limited.
A summary of maximum RQs for triclopyr across use sites is detailed in Appendix A.
Terrestrial Risks
Mammals
There are potential acute risks of concern to mammals with RQs ranging from <0.01 to 1.5 (level
of concern, or LOC = 0.5) from all four triclopyr forms assessed (acid, TEA, COLN, and BEE).
There are risk exceedances for non-crop areas and utility or road rights-of-way applications,
which were assessed at the 6-9 lb ae/A rates. In the 2019 ecological risk assessment, pastures and
rangeland uses, which were assessed at a maximum rate of 9 lb ae/A for only spot treatment of
grazable lands that intersect with non-crop areas, also exceeded the LOC. At a maximum rate of
2.0 lb ae/A (which are for both spot treatment and wide area broadcast applications to
pasture/rangeland), there are no acute risks of concerns for mammals.
There are potential chronic risks of concern to mammals from the four triclopyr forms assessed
with RQs ranging from 0.02 to 37.0 (LOC = 1.0). Chronic adverse effects observed in the 2-
generation rat reproduction study included a 28 to 39% reduction in litter size, a 29 to 32%
reduction in body weights for offspring, and a 17% reduction in pup survival. There are potential
chronic risks of concern for the following uses: rice, turf, forestry, non-crop areas and rights of
ways, and applications to pasture/rangeland at 2 lb ae/A or higher.
9	Unites States Department of Agriculture (USD A). 2020. Public Comment received from the USD A, Docket ID
EPA-HQ-OPP-2014-0576-0030. Available at: hHps://www.regulations.gov/document?D=EPA-HO-OPP-2Q14-
0576-0030
10	USDA OPMP. 2020. Personal communication via e-mail with the United States Department of Agriculture Office
of Pest Management Policy.
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Birds. Reptiles, and Terrestrial-Phase Amphibians
There are potential acute risks of concern to birds from the four triclopyr forms assessed with
RQs ranging from <0.01 to 4.6 (acute risk LOC = 0.5). Acute dose-based RQs exceed the LOC
for all uses but rice. Acute dietary-based RQs do not exceed the LOC with the exception of
rights-of-way uses, where RQs are marginally above the acute risk LOC (max RQ = 0.74). Acute
risks to birds are mostly associated with uses that have high maximum application rates (forestry,
non-crop areas, and rights of ways, where application rates are 6.0- 9.0 lb ae/A).
There are potential chronic risks of concern to birds from the assessed triclopyr forms with RQs
ranging from 0.09 to 22 (LOC = 1.0) and there are risk exceedances for all uses. The chronic
effect found was a 14% reduction in number of survivors. The higher chronic RQs (14 for
forestry and 22 for non-crop areas and rights of ways) are mostly associated with high
application rates between 6.0 - 9.0 lb ae/A. Chronic RQs up to 4.8 also exceed the LOC for
applications to pasture/rangeland at 2.0 lb ae/A or above.
Terrestrial Invertebrates (honey bees)
The following uses were assumed to have possible exposure to pollinator attractive plants:
residential turf (assuming the presence of blooming weeds), forestry, non-crop areas/rights of
ways, and pasture/rangeland. The Tier 1 suite of laboratory-based acute and chronic toxicity
data are available for triclopyr except for acute oral toxicity data for honeybee larvae11. The 8-
day LDso value (i.e., dose at which 50% of the test population dies) from the available 22-day
chronic larval toxicity study was utilized as a surrogate acute larval toxicity value in the risk
assessment. While EPA did not identify risks of concern for acute contact exposure of adult
honey bees, the Tier I assessment concludes that there is potential chronic risks of concern to
adult bees (chronic adult RQs range from 2.3-20, based on 35% reduction in adult survival) and
potential chronic risks of concern to larval bees (chronic larval RQs range from 23-211, based on
10%) reduction in emergence and 13% reduction in mortality). Potential chronic risks of concern
to honeybees are indicated for all registered uses of triclopyr for triclopyr acid. Nine
bee incidents have been reported for triclopyr, primarily associated with triclopyr TEA and BEE.
The Agency assessed risk beyond the edge of the treated area to below toxicity threshold for
adult bees and larval bees. For adult bees, potential chronic risks of concern extend from 7-184
feet from the application area, depending on the use pattern and the application rate. For larvae,
potential chronic risks extend to 220 ft from the application area for turf use, and greater than
1,000 feet for forestry, parks, campgrounds, and rights-of-way uses.
While chronic RQs for bees exceed the LOC for both adults and larvae, triclopyr is not applied to
crops contracted for pollination services. Many of the uses for triclopyr are to non-pollinator
attractive sites such as rice, aquatic weeds, industrial non-cropland sites, and as stump treatment
for trees. There is possible exposure to pollinator attractive plants from applications to
pasture/rangeland, forestry, rights-of-ways, and turf sites with flowering plants. The exposure to
11 An acute oral toxicity larval honeybee study report has been received and will be included in future analyses.
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bees from these applications is likely to be spatially and temporally limited. The application of
triclopyr will also likely cause the death of the target plant, which narrows the window of time
that blooming flowers would be available for foraging.
Given the pollinator risk concerns identified at the Tier I level for triclopyr, additional Tier II
honeybee data are needed for triclopyr acid. A Tier II semi field testing requirement for
pollinators (tunnel or colony feeding) study and Tier II field trial of residues in pollen and nectar
study were included in the data call in (GDCI-116001-1546) and are needed based on the results
from Tier I testing. These higher-tier data will help to refine the understanding of potential
exposure of bees from these registered uses of triclopyr acid/TEA/COLN, and the extent of risk
at the colony level.
For triclopyr BEE, available laboratory and field-based fate studies indicate rapid transformation
of triclopyr BEE to triclopyr acid in soil and aquatic systems (e.g., half life < 1 day). However,
the rate of transformation of triclopyr BEE in (or on) plant tissues is uncertain. Should triclopyr
BEE rapidly transform to the acid form in plant tissues, then no additional bee toxicity data
would be needed for triclopyr BEE, because exposure and risk assessment would be based on the
acid form. Available plant metabolism data for triclopyr are restricted to rice, which does not
produce honeybee attractive nectar or pollen. However, if triclopyr BEE remains in (or on) bee-
relevant plant tissues for durations considered toxicologically relevant (e.g., several days),
additional Tier 1 honeybee toxicity data may be needed for triclopyr BEE. Therefore, data on
the magnitude and persistence of triclopyr BEE in pollen and nectar is needed to refine the
understanding of potential exposure of bees from these registered uses of triclopyr BEE.
Terrestrial Plants
As expected from an herbicide, there are potential risks of concern for terrestrial plants. Risks
exceed the level of concern for all uses. Terrestrial plant RQs ranged from <0.1 to 17 for ground
spray (where RQs above 1.0 exceed the LOC). RQs for aerial application also exceeded the LOC
and ranged from 0.16 to 83. The Agency used spray drift modeling to determine the distance
from the edge of the application where residues are below the toxicity threshold for both ground
and aerial application. Risks extend from 14 to over 1,000 feet from the edge of the treated area
for ground applications, and from 112 to over 1,000 feet from the edge of the treated area for
aerial applications. Additionally, 49 terrestrial plant spray drift incidents have been reported to
the Agency.
Compost Contamination
Crop injuries have been reported from mulch, grass clippings, straw/hay, manure, and compost
contaminated with some pyridine herbicides. Depending on fate properties of the herbicide and
environmental conditions, breakdown can occur in as few as 30 days, but some field reports
indicate that breakdown can take as long as years. The herbicides of greatest concern are
aminocyclopyrachlor, picloram, clopyralid, and aminopyralid because they can remain active in
hay, grass clippings, piles of manure and compost for a long time. There are reported incidents of
non-target plant damage from residues of pyridine herbicides in compost. These herbicides
eventually break down through exposure to sunlight, soil microbes, heat, and moisture.
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There have been no compost incidents reported with triclopyr alone. There is one compost
incident involving a product containing both triclopyr and clopyralid, however it is unknown
whether this incident is due to the presence of triclopyr or clopyralid or the interaction of both
(incident number 1012701-001, see Appendix C of the ecological risk assessment for more
information). There are data gaps for this route of exposure and uncertainty with respect to how
triclopyr will dissipate and persist in compost.
Due to persistence concerns for synthetic auxin pyridine herbicides, additional data are needed to
assess the persistence of triclopyr in compost, the compost studies needed are:
	A non-guideline compost kinetics study for vegetative material and manure
	A modified guideline 835.6100 terrestrial field dissipation study that lasts 30 days
	A non-guideline compost bioassay study for both vegetative material and manure.
Aquatic Risks
Fish
No acute risks of concern were identified from any uses of triclopyr across all the forms
assessed. There were no chronic risks of concern to fish with the exception of chronic risks to
freshwater fish from the highest application (5,000 ppb) of triclopyr acid/TEA/COLN for aquatic
weed control (RQ=1.8, LOC=1.0). The chronic effect seen was a 3% and 6% reduction in mean
length and weight of fish.
Aquatic Invertebrates
No acute risks of concern were identified from any uses of triclopyr across all forms assessed.
Chronic risks of concern are identified for freshwater invertebrates for the aquatic weed control
use at the two highest application rates, 2,500 and 5,000 ppb of triclopyr acid/TEA/COLN, with
RQ values of 3.0 and 6.0 respectively. The chronic effect seen was a 15 to 58% reduction in
young females. For citrus stump treatment application, the RQ was identical to the LOC
(RQ=1.0, LOC=1.0) for saltwater invertebrates in the water column.
Aquatic Plants
The aquatic plant LOC of 1.0 is exceeded slightly for non-vascular aquatic plants for aquatic
weed control with triclopyr acid/TEA/COLN at the highest rate (5,000 ppb, RQ=1.2, LOC=1.0),
and for citrus stump treatment (RQ=1.4, LOC=1.0). Although risk was indicated to non-vascular
aquatic plants at the 9 lb ae/A rate assessed for rangeland/pasture, risks are not indicated at an
application rate of 2 lb ae/A (which is the limit for wide area broadcast treatments to pasture and
rangeland). Stump treatments and pasture/rangeland treatments at the 9 lb ae/A rate are spot
treatments and are highly localized, as noted previously.
For aquatic vascular plants, no risk exceedances were identified with any triclopyr product
assessed. However, the tested species (i.e., duckweed) may differ in its sensitivity compared to
rooted vascular plants, particularly targeted aquatic weeds, in part due to its different physiology.
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Therefore, there may be some uncertainty for risk to vascular aquatic plants, particularly since
triclopyr acid, TEA and COLN are registered for control of aquatic weeds.
Ecological Incidents
The Incident Data System (IDS) provides information on the available ecological pesticide
incidents. A search of the Incident Data System (IDS) for triclopyr was conducted in May 2019.
There are over 100 reported individual incidents from 1990 to 2019 in which triclopyr acid,
TEA, or BEE products were applied and implicated in adverse effects to non-target organisms.
Incidents are categorized according to the likelihood that use of triclopyr was associated the
incident, and the classification categories are: unrelated, unlikely, possible {i.e., the pesticide
possibly could have caused the incident but there are other possible explanations), probable {i.e.,
circumstances indicate that the pesticide was the cause, but confirming evidence is lacking), and
highly probable {i.e., pesticide was confirmed as the cause through reliable evidence). Most
incidents involved damage to non-target terrestrial and aquatic plants and were considered
probable or possible in their causality classification. Nine incidents involved losses of honeybee
hives and although triclopyr products were reported as being used in nearby areas, exposures
were not verified by residue analysis. In no cases were bees killed immediately, but eventually
{i.e., over time) hives failed. Two incidents involved fish kills near a rice field and a railroad
crossing adjacent to a river. These fish incidents were classified as probable, but mortality was
potentially from secondary effects (oxygen depletion from algae die off). In many of the
triclopyr incidents, other herbicides were also used on site or triclopyr was applied as part of a
mixed product containing another pesticide, so incidents could not be attributed to triclopyr
alone. This was the case for one "probable" incident involving compost in 2002, where tomato
seedlings exposed to contaminated compost showed stunted growth and leaf splitting.12
Triclopyr and clopyralid were implicated in the compost contamination but it was uncertain
which pesticide or if the interaction of both pesticides caused the plant damage.
The Agency will continue to monitor ecological incident information as it is reported to the
Agency. Detailed analyses of these incidents are conducted if reported information indicates
concerns for risk to non-target organisms.
2. Ecological and Environmental Fate Data Needs
In support of registration review for triclopyr, a generic data call-in (GDCI-116001-1546) was
issued, requiring the submission of several environmental fate and ecotoxicity studies. All
required studies have been satisfied except for a guideline 850.2100 study and tier II honey bee
studies. Guideline 850.2100 (avian acute oral toxicity study with a passerine bird) has been
submitted and is currently in review. As previously noted, the results of Tier I honey bee risk
assessment indicates chronic risk to larval and adult honey bees. The registration review GDCI
noted that the requirement for higher tiered honeybee studies were dependent on the results of
Tier I testing. The Agency concludes that these Tier II studies are needed in support of
registration review for triclopyr acid:
 a non-guideline field trial of residues in pollen and nectar and
12 See incident number 1012701-001 in Appendix C of the triclopyr ecological risk assessment.
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 a non-guideline semi-field testing for pollinators (tunnel or colony feeding).
EPA will evaluate these pollinator studies and determine if addition pollinator data needs to be
generated.
As mentioned above, in addition to the data required by GDCI-116001-1546, the following
studies are needed to better understand the potential for triclopyr to contaminate compost:
	a modified guideline 835.6100 terrestrial field dissipation study with a duration of at least
30 days,
	a non-guideline compost kinetics study for vegetative material and manure, and
	a non-guideline compost bioassay studies for both vegetative material and manure.
C. Benefits Assessment
Use of triclopyr provides benefits in both agricultural and non-agricultural settings. Triclopyr
provides benefits to users in pasturelands and rangeland due to its excellent control of numerous
woody and broadleaf weed species, such as mesquite and catclaw, that are commonly
problematic in these sites. A unique benefit of pyridine herbicides, such as triclopyr, is that they
are more selective compared to other effective broad-spectrum herbicides. This characteristic
allows land managers to maintain desirable forage and shrub species in the landscape to serve as
shade and forage for grazing livestock. Triclopyr is used as a cut-stump and basal bark
application in these settings to control dogfennel, honeysuckle, blackberry, honey-locust,
buckeye, oaks, willow pine, sumac, mixed brush, and other undesirable plants. Alternatives used
in pasture/rangeland management are other pyridine herbicides, such as picloram and clopyralid.
Triclopyr is considered essential by the United States Forest Service13 for the control of invasive
plant species such as bush honey suckle, tamarisk, and Siberian elm in the management of public
lands. The USDA Animal and Plant Health Inspection Service14 noted benefits as well as for
stump and root removal in control attempts for invasive insect species including Asian long-
horned beetle and spotted lanternfly. Triclopyr is also important for conifer site preparation and
conifer release treatments and offers selective control so it does not damage desirable tree
species while controlling undesirable weeds and shrubs.
Triclopyr is also used by private foresters for site preparation, stand management, and habitat
management in silviculture. Private foresters like triclopyr for its versatility and its specificity.
Triclopyr is used to control noxious or invasive plants and to control un-wanted brush in the
forest understory. In the southeast and northeast, triclopyr is mainly applied by helicopter in
timber stands that are too remote to access with vehicles or applied by vehicle-mounted
mechanically pressurized handgun or backpack sprayer. Alternatives in forestry management
are: aminopyralid, glyphosate, hexazinone, imazapyr, and sulfometuron-methyl.
13	See information from the United States Forest Service in the triclopyr registration review docket (EPA-HQ-OPP-
2014-0576), available at: httDs://beta.regulations.gov/document/EPA-HO-OPP-2014-0576-0039
14	See comment submitted by USDA in triclopyr registration review docket (EPA-HQ-OPP-2014-0576), available
at: https://befa.regiilations.gov/coniment/EPA-HO-OPP-2014-0576-0030
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In golf courses and other turf sites, triclopyr is considered safe for use on a variety of turfgrass
species for the selective postemergence control of numerous annual and perennial broadleaf
weed species. Alternative herbicides used in turf management are 2,4-D, dichlorprop, mecoprop,
dicamba, and clopyralid.
In non-croplands, triclopyr is recommended for the control of broadleaf weeds, vines, brush, and
trees using foliar treatment, basal bark, cut surface, and cut stump applications. Selective control
is more important in non-cropland use sites such as fencerows and rights-of-way as opposed to
industrial sites which are often left bare ground. These areas can contain both desirable and non-
desirable plants which makes the use of a selective herbicide like triclopyr important. Other
selective herbicides used in non-cropland settings include picloram and dicamba. Other
herbicides used for basal bark applications in these areas include 2,4-D; however, triclopyr has
really become the primary herbicide for this application method since it is a more selective
chemical that prevents damage to nearby desirable tree species. For additional information on the
benefits of triclopyr, see the document Usage, Benefits and Alternatives for Triclopyr.
IV. INTERIM REGISTRATION REVIEW DECISION
A. Risk Mitigation and Regulatory Rationale
The Agency has reviewed the risks and benefits associated with the registered uses of triclopyr
in developing this Interim Registration Review Decision. EPA has determined that the only
potential human health risk of concern is to occupational handlers mixing/loading liquid products
for aerial forestry applications. To mitigate this risk EPA has determined it is necessary for a PF-
10 respirator to be worn by mixers and loaders for aerial application via helicopter for forestry
use.
The Agency identified potential risks to non-target terrestrial plants from spray drift and runoff.
There were also potential risks to mammals, birds, terrestrial invertebrates, aquatic invertebrates,
and aquatic plants. It is necessary for mandatory spray drift management measures to be put on
labels to reduce risks to non-target organisms.
Triclopyr is a synthetic auxin and has structural similarity to other pyridine herbicides with
known compost incidents. The potential for triclopyr to persist in compostable plant material
and manure and pose risks of concern is an uncertainty. The Agency is adding compost labeling
for certain persistent herbicides based on a weight of evidence approach. Based on its toxicity to
non-target terrestrial plants, its fate properties (it is highly mobile, is stable to hydrolysis, and can
leach to groundwater), and its structural similarity to herbicides known for compost
contamination, it is necessary for product labels to reflect new labeling intended to prevent
treated plant materials from entering the compost stream. EPA is also planning to call in
additional data for triclopyr to evaluate the potential for compost contamination. Further, it is
necessary that labels provide herbicide resistance management information and that registrants
update all labels to meet current standards.
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1. Respirator for Mixers/Loaders for Aerial Forestry Use
To mitigate potential inhalation risk to occupational handlers, a respirator for pesticides covered
by the Worker Protection Standard15 (WPS), and the associated fit test, training, and medical
evaluation is necessary for the following scenario:
 mixers and loaders using liquid products in aerial forestry applications via helicopter
Fit testing, training, and medical evaluations16 are necessary for all handlers who are required to
wear respirators for aerial forestry applications via helicopter.17 If a triclopyr handler currently
does not use a respirator, an additional cost will be incurred by the handler or the handler's
employer, which includes the cost of the respirator plus, for WPS-covered products, the cost for
a respirator fit test, training, and medical exam.
Respirator costs are extremely variable depending upon the protection level desired,
disposability, comfort, and the kinds of vapors and particulates being filtered. Based on available
information, the cost of the respirators (whether disposable or reusable) is relatively minor in
comparison to the fit-test requirement under the Worker Protection Standard. The Agency
expects that the average cost of a particulate filtering facepiece respirator is lower than the
average cost of an elastomeric half mask respirator. In 2015, the estimated cost of a respirator fit
test, training and medical exam is about $180 annually.18 However, if a triclopyr handler
typically uses other chemicals requiring a respirator in the production system or as part of the
business, additional fit testing is not needed. The handler or employer may only incur the cost of
purchasing filters for the respirator on a more frequent basis. Respirator fit tests are currently
required by the Occupational Safety and Health Administration (OSHA) for other occupational
settings to ensure proper protection.19
The EPA acknowledges that requiring a respirator and the associated fit testing, training, and
medical evaluation places a burden on handlers or employers. However, the proper fit and use of
respirators is essential to accomplish the protections respirators are intended to provide. In
estimating the inhalation risks, and the risk reduction associated with different respirators, the
EPA's human health risk assessments assume National Institute for Occupational Safety and
Health (NIOSH) protection factors {i.e., respirators are used according to OSHA's standards). If
the respirator does not fit properly, use of triclopyr may cause unreasonable adverse effects on
the pesticide handler.
15	40 CFR 170
16	Fit testing, training, and medical evaluations must be conducted according to OSHA regulations 29 CFR 
1910.134, 29 CFR  1910.134(k)(l)(i) through(vi), and 29 CFR  1910.134, respectively.
17	40 CFR 170 (see also Appendix A of Chapter 10 of the Label Review Manual, available at
https://www.epa.gi3v/pesficicie-regisfration/label-review-mannan
18	Economic Analysis of the Agricultural Worker Protection Standard Revisions. Biological and Economic Analysis
Division, Office of Pesticide Programs, U.S. EPA. 2015. p. 205. Available at www.regiilations.gov. docket number
EPA-HQ-OPP-2011-0184-2522
19	29 CFR S 1910.134
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With the addition of a respirator for mixers and loaders for triclopyr aerial forestry applications
via helicopter, there are no risks of concern for other occupational handler scenarios. The
addition of a respirator for this use also potentially reduces the need for a subchronic inhalation
toxicity study. With the exception of the costs outlined above associated with training, fit
testing, and medical exam, the addition a respirator is expected to cause minimal economic
impact on users. Aerial forestry application via helicopter is geographically limited and
mixers/loaders for aerial application would likely already have access to respirators.
2. Updated Gloves Statement
It is necessary to update the gloves statements to be consistent with Chapter 10 of the Label
Review Manual. In particular, it is necessary for the removal of references to specific categories
in EPA's chemical-resistance category selection chart and that labels specify the appropriate
glove types to use. For example, this statement from the label is to be removed:
"For more options, follow the instructions for Category A on the chemical-resistance
category selection chart."
3. Measures to Address Potential Compost Concerns
Triclopyr is a pyridine herbicide and a synthetic auxin. Some herbicides in the pyridine class
have been found to persist in compost and there are reported incidents of damage to non-target
terrestrial plants. Herbicides such as aminopyralid, picloram, and clopyralid have been found to
persist at phytotoxic levels for long periods of time, from months to years. Pyridine herbicides
can contaminate compost via treated plant material or manure from animals that have grazed on
treated areas that then enters a composting facility. Once a compost facility is contaminated it
can impact many end users through the sale of this compost. Residues in contaminated compost
can cause stunting or abnormal growth of plants exposed to the compost.
Currently there are limited data on the persistence of triclopyr in compost, and there have been
no reported incidents of compost contamination involving triclopyr alone. There is one incident
reported of non-target plant damage from compost involving a mixed triclopyr and clopyralid
product, but there are additional compost incidents reported with clopyralid. However, the low
number of incidents does not necessarily indicate that there is no potential risk of compost
contamination. The Agency is considering compost labeling for some synthetic auxins based on
a weight of evidence approach, which include the following considerations:
o Incident data,
o Fate data indicating stability to hydrolysis and high mobility (i.e., ability to leach from
finished compost),
o Toxicity to non-target terrestrial plants,
o Structural similarity to pesticides with known compost issues, and other lines of
evidence.
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Based on triclopyr's fate properties such as its ability to leach and it being highly mobile, its
toxicity to non-target terrestrial plants, and its structural similarity to herbicides with known
compost issues, the Agency concludes that triclopyr may have the potential to contaminate
compost. To address potential composting concerns, a statement instructing users not to transport
offsite treated plant materials (e.g., hay, turf clippings) or manure from animals that have grazed
in treated areas for compost until 30 days after application is necessary. A clean out period for
livestock that have grazed on treated lands is also necessary. EPA is also only requiring this
compost mitigation language and animal clean out time on labels with pasture and turf uses,
since these uses sites are thought to be most likely to attribute treated materials to the compost
stream. The following compost statements are required for pasture and turf uses:
"This product is persistent and may be present in treated plant materials for over 30 days after
application. Do not sell or transport treated plant materials or manure from animals that have
grazed on treated plant materials off-site for compost distribution or for use as animal
bedding/feed for 30 days after application.
Animals that have been fed triclopyr treated forage must be fed forage free of triclopyr for at
least 3 days before movement to an area where manure may be collected, or sensitive crops are
grown."
The Agency assessed the potential impacts to triclopyr users from these restrictions. Users may
experience increased difficulty in disposing of hay, grass clippings, and excess manure.
Livestock managers may have to treat only a portion of a site to have an adequate untreated area
for livestock to graze in during the 3-day clean out period or may have to provide additional
forage. Users might switch to an alternative without compost restrictions, which could be more
costly and less efficacious. The magnitude of the impacts on individuals is uncertain and may be
highly variable depending on circumstances.
The EPA needs compost data for triclopyr to improve our understanding of the potential for
compost contamination. Compost data being required are:
o a modified guideline 835.6100 terrestrial field dissipation study with a duration of at least
30 days,
o a non-guideline compost kinetics study for vegetative material and manure, and
o a non-guideline compost bioassay study for both vegetative material and manure
The Agency will review the need for compost labeling in future decisions, considering any new
compost data available. The results from the on-field dissipation study will determine if the
compost kinetics and compost bioassay studies are needed. If on-field dissipation study shows
that residues dissipate rapidly after application and are not of concern, the compost kinetics and
compost bioassay studies are not needed.
4. Spray Drift Management
Label changes to reduce off-target spray drift and establish a baseline level of protection against
spray drift that is consistent across all triclopyr products are necessary. Reducing spray drift will
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reduce the extent of environmental exposure and risk to non-target plants and animals. Although
the Agency is not making a complete endangered species finding at this time, these label changes
are expected to reduce the extent of exposure and may reduce risk to listed species whose range
and/or critical habitat co-occur with the use of triclopyr.
The following spray drift mitigation language is to be included on all triclopyr product labels for
products applied as liquid spray application. The spray drift language is intended to be
mandatory, enforceable statements and supersede any existing language already on product
labels (either advisory or mandatory) covering the same topics. The Agency is also providing
recommendations which allow triclopyr registrants to standardize all advisory language on
triclopyr product labels. Registrants must ensure that any existing advisory language left on
labels does not contradict or modify the new mandatory spray drift statements necessary for this
ID, once effective.
	Applicators must not spray during temperature inversions.
	For aerial applications, do not apply when wind speeds exceed 15 mph at the application
site. If the windspeed is greater than 10 mph, the boom length must be 65% or less of the
wingspan for fixed wing aircraft and 75% or less of the rotor diameter for helicopters.
Otherwise, the boom length must be 75% or less of the wingspan for fixed-wing aircraft
and 90% or less of the rotor diameter for helicopters.
	For aerial applicators, if the windspeed is 10 miles per hour or less, applicators must use
'/2 swath displacement upwind at the downwind edge of the field. When the windspeed is
between 11-15 miles per hour, applicators must use 3/4 swath displacement upwind at the
downwind edge of the field.
	For aerial applications, the release height must be no higher than 10 feet from the top of
the crop canopy or ground, unless a greater application height is required for pilot safety.
	For ground boom applications, apply with the release height no more than 4 feet above
the ground or crop canopy.
	For ground boom-less application (e.g., roadsides, rights of ways) there will be no
mandatory release height restrictions due to equipment having physical limitations for
achieving a height of 4 feet. There will be advisory spray drift language informing
applicators to set nozzles at the lowest effective height to help reduce the potential for
spray drift. The droplet size for these applications are also typically coarser, thus
reducing the risk of spray drift.
	For ground applications, do not apply when wind speeds exceed 15 miles per hour at the
application site.
	Applicators are to select a nozzle and pressure combination that delivers a medium or
coarser droplet size (AS ABE S572 for ground applications and AS ABE S641 for aerial
applications).
In addition to including the spray drift restrictions on triclopyr labels, all references to volumetric
mean diameter (VMD) information for spray droplets are to be removed from all triclopyr labels
where such information currently appears. The new language above, which cites ASABE S572
for groundboom equipment and ASABE S641 for aerial equipment, eliminates the need for
VMD information.
Impacts of Syr ay Drift Mitigation
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Temperature Inversion
The requirement could result in delays to intended applications and, more generally, reduce the
amount of time users have to apply triclopyr. Potentially, growers could switch to a different
active ingredient that does not have this restriction, but that would be costly and potentially
difficult to obtain in a short period of time.
Wind Speed
A 15-miles per hour (mph) wind speed restriction for ground and aerial applications of triclopyr
is being required for all labels. Some, but not all triclopyr labels currently contain these wind
speed restrictions and therefore some users may be impacted by the requirement. Wind
conditions vary across the U.S. and wind speed restrictions could prevent timely applications of
triclopyr. Survey data (Bish and Bradley, 2017)20 indicate that most applicators consider wind
speed when making applications and typically apply at wind speeds of 15 mph or lower.
However, there are situations when applicators will spray at wind speeds greater than 15 mph
(these applicators account for less than 10% of survey respondents). Mandatory wind speed
restrictions potentially complicate weed and crop management by reducing the available time to
make applications and make it more likely that a grower may need to alter pest control plans.
Users may switch to other products that do not have this restriction if they regularly encounter
wind speeds over 15 mph during the application season.
The Agency also notes that some users have already limited use of pesticides during low wind
speeds. For instance, nursery, ornamental and turf applicators generally have mixtures of many
plant species in the general application area and must be precise in application to avoid off-site
movement and resulting phytotoxicity damage to their stock. Therefore, impacts of the a
windspeed restriction may be minimal to these users because they would normally apply only
under relatively calm conditions.
Release Height
Triclopyr labels do not have any required maximum release height for ground boom applications.
Spray release height is important to minimize overlap of spray from nozzles while maintaining
proper coverage. If nozzles are placed too low, the application may not provide adequate
coverage which could lead to portions of the field not receiving pesticide. The Agency reviewed
manufacturer recommendations and found21 that a release height of 4 feet allows adequate
20
Bish, M. and K.W. Bradley. 2017. Survey of Missouri Pesticide Applicator Practices, Knowledge, and
Perceptions. Weed Technology 31:165-177. Available at:
https://weedscience.niissonri.edu/Pesticide%20Applicator%20Knowledge	[
21	Tindall, K. and C. Hanson. 2018. Qualitative Benefits and Usage Assessment of Diflufenzopyr (PC Code
005108) and Diflufenzopyr-Sodium (PC Code 005107). Available at:
https://www.regulations.gov/document?D=EPA-HO-OPP-2Ql.1.-09.1. .1.-0022
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coverage for the majority of nozzles. Therefore, the EPA does not anticipate any negative
impacts to growers from the requirement.
For aerial applications, the Agency considers a release height of 10 feet from the top of the crop
canopy or ground to be standard application practice and does not anticipate any negative
impacts from the requirement.
Droplet Size
The Agency is establishing a mandatory droplet size of "medium or coarser," as defined by
AS ABE S572 for groundboom equipment and AS ABE S641 for aerial equipment, for triclopyr.
Currently triclopyr labels have only advisory language for droplet size. Based on a previous 2017
Agency analysis22, several factors (e.g., droplet formation at the nozzle, retention on the leaf
surface, deposition of the active ingredient, the resulting biological response, environmental
conditions, etc.) can impact the efficacy of an herbicide application, including droplet size.
Generally, the Agency concludes there will be lower impacts associated with larger droplet sizes
(i.e., medium or coarser) with systemic herbicides than with contact herbicides in regard to
efficacy. However, despite being translocated in plants, triclopyr must contact foliage for
effective weed management. Therefore, requiring medium or coarser droplets may affect the
efficacy of triclopyr when triclopyr is used alone.
A droplet size of medium or coarser could reduce the flexibility of pesticides co-applied with
other pesticides (e.g., herbicides, insecticides) that require a smaller droplet size, requiring
farmers to make two separate applications (one for each droplet size) or reducing efficacy of
other pesticides co-applied with triclopyr that require smaller droplet sizes to be effective. If
reduced efficacy occurred with tank mixed herbicides or insecticides, the Agency would expect
growers to respond by increasing the application rates (if allowed by the label), increasing the
number of applications, increasing the application rates of tank mix partners, making additional
herbicide applications with other herbicides, or changing to a different herbicide.
5. Non-Target Organism Advisory
The Agency is also adding a non-target organism advisory on labels. The protection of
pollinating organisms is a priority for the Agency. Use of triclopyr may negatively impact forage
and habitat of pollinators and other non-target organisms. It is the Agency's goal to reduce spray
drift whenever possible and to educate growers on the potential for indirect effects on the forage
and habitat of pollinators and other non-target organisms. Therefore, a non-target organism
advisory language is necessary to be placed on triclopyr's labels to address this potential
concern. See Appendix C for the statement.
22 Chism, B., J. Becker, C. Hawkins, and S. Smearman. 2017. Effects of Mandatory Spray Droplet Size Category on
Herbicide Efficacy and Crop Yield: Potential Impacts on Sulfonylurea-Registered Crops.
hHps://www.regulations.eov/document?D=EP A-HO-OPP-20.1. .1.-0994-0057
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6. Herbicide Resistance Management
On August 24, 2017, the EPA finalized a Pesticide Registration Notice (PRN) on herbicide
resistance management.23 Consistent with the Notice, the implementation of herbicide resistance
measures for existing chemicals during registration review, and for new chemicals and new uses
at the time of registration is necessary. In registration review, herbicide resistance elements will
be included in every herbicide ID.
The development and spread of herbicide resistant weeds in agriculture is a widespread problem
that has the potential to fundamentally change production practices in U.S. agriculture. While
herbicide resistant weeds have been known since the 1950s, the number of species and their
geographical extent, has been increasing rapidly. Currently there are over 250 weed species
worldwide with confirmed herbicide resistance. In the United States, there are over 155 weed
species with confirmed resistance to one or more herbicides.
Management of herbicide resistant weeds, both in mitigating established herbicide resistant
weeds and in slowing or preventing the development of new herbicide resistant weeds, is a
complex problem without a simple solution. Coordinated efforts of growers, agricultural
extension, academic researcher, scientific societies, pesticide registrants, and state and federal
agencies are required to address this problem.
The EPA is requiring measures for the pesticide registrants to provide growers and users with
detailed information and recommendations to slow the development and spread of herbicide
resistant weeds. This is part of a more holistic, proactive approach recommended by crop
consultants, commodity organizations, professional/scientific societies, researchers, and the
registrants themselves.
7. Environmental Hazards
a.	Fish and Aquatic Invertebrates Statement for BEE Products
On an acute exposure basis, triclopyr BEE is consistently 2 to 3 orders of magnitude more toxic
to aquatic animals compared to triclopyr acid or TEA. This has led to many triclopyr BEE
product labels having an aquatic organism hazard statement. The Agency has determined that it
is necessary to apply this statement across all the triclopyr BEE labels. The statement will warn
that the product may be hazardous to fish and aquatic invertebrates. Please see Appendix C for
the full statement.
b.	Aquatic Weed Control Statement
23 PRN 2017-2, "Guidance for Herbicide Resistance Management Labeling, Education, Training, and Stewardship".
Available at https://www.epa.gov/pesficide-regisfrafion/pesficicie-regisfration-nofices-vear
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Some triclopyr products are used to treat invasive aquatic plants and other aquatic weeds. In
accordance with guidance in EPA's label review manual, an aquatic weed control statement is
necessary for all triclopyr products with direct applications to water. The aquatic weed control
statement will warn users of the potential for fish suffocation from oxygen loss from
decomposition of dead weeds and require applicators to not treat more than half of the water
body in a single application and wait at least 14 days between treatments. It also instructs
applicators to begin treatment along the shore and proceed outward in bands to allow for fish
movement. Please see Appendix C for the full statement.
c.	Surface Water Advisory
Triclopyr has been detected in surface water monitoring data. Triclopyr's fate properties
suggest that it has a high potential to reach surface water. For this reason, it is necessary for a
surface water advisory to be placed on all triclopyr labels to address this potential concern. The
statements are consistent with guidance in EPA's label review manual. Non-agricultural labels
will need to have a general statement that the triclopyr product can impact surface water quality
through runoff. For products with agricultural uses, additional advisory text is needed on the
benefits of vegetated buffer strips and avoiding applications within two days of expected rainfall
or irrigation. The statements are noted in Appendix C.
d.	Ground Water Advisory
Triclopyr has been detected in groundwater monitoring data. In addition, triclopyr has
environmental fate properties that indicate it has the potential to persist in groundwater. For this
reason, a groundwater advisory is necessary to be placed on all triclopyr labels to address this
potential concern. This language will warn that triclopyr products have the potential to leach into
groundwater. Please see Appendix C for the full statement.
8. Clarification of Application Rates
a. Grazable Areas Intersecting with Treated Non-Cropland, Rights of Way,
and Forestry sites
The triclopyr labels include a 2 lb ae/A per season maximum application rate for pasture,
rangelands, and any other areas which are grazed. Some labels have an exception that allow for
higher application rates (up to 8 lb ae/A) in grazed areas that intersect treated non-cropland,
rights-of-way, and forestry sites if the application comprises no more than 10% of the total
grazable area. The intention of this exception is to allow for applicators to make spot treatments
on public easements. Language on current labels read as follows:
"Portions of grazed areas that intersect treated non-cropland, rights-of-way and forestry sites
may be treated at up to 8 lb ae per acre if the area to be treated on the day of application
comprises no more than 10% of the total grazable area."
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The current text may be unclear for some users. The Agency has determined that it is necessary
for the existing language to be revised to clarify the maximum single application rate for non-
cropland, rights-of-way, and forestry sites that intersect grazed areas:
"The maximum application rate for spot treatments on non-cropland, rights-of-way, and forestry
sites that intersect grazed areas is 8 lb ae /A/year. Spot treatment applications at rates over 6 lb
ae/A must not use aerial or broadcast ground boom application equipment."
b. Maximum Application Rates
Some labels lack adequate information on the maximum application parameters. Labels
frequently do not specify the maximum yearly rate and list only seasonal rates. EPA needs
labels that include clear maximum single rates, maximum yearly rates, and minimum retreatment
intervals. In discussions with the Agency on May 6, 2020, Corteva Agriscience, one of the
technical registrants for triclopyr, notes that the information noted in Table 3 are the maximum
application parameters being supported for uses on the labels:
Table 3. Maximum App
ication Parameters by Use Site
Use site
Maximum single
application rate (lb
ae/A)
Maximum yearly
application rate (lb
ae/A)
Minimum retreatment
interval (days)
Pasture and rangeland
2
2
28
Spot treatment on
non-cropland, rights
of way, and forestry
sites that intersect
grazed areas (e.g.,
public easements)
8
8
28
Forestry
6
6
28
Non-crop areas
(including rights of
ways, fencerows, and
similar areas) for
triclopyr TEA
9
9
28
Non-crop areas
(including rights of
ways, fencerows, and
similar areas) for
triclopyr BEE
8
8
28
Turf and ornamentals
1
4
28
Foliar applications to
floating/emerged
weeds in aquatic
water bodies
6
6
14
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No additional comments were received on these rates during the PID public comment period and
the Agency expects limited impact from the label clarifications, as the current use parameters are
not being altered. The 2 lb ae/A per season rate for pasture/rangeland needed to be converted to
a yearly rate, but this change is not expected to have impact on users because pasture and
rangeland are typically perennial cropping systems and therefore a seasonal rate is equivalent to
an annual rate.
c. Aquatic Applications
For direct applications to water for aquatic weed control, some of the labels do not specify the
average depth/area of the water body or lb ae/A-foot of water to be treated to arrive at the
effective concentration necessary to kill weeds. The rates for aquatic weed control should include
the appropriate units associated with these applications (acre-foot) and also reflect the
appropriate depth and area of the water body to help add clarity to the label. The addition of a
table that provides information on rates expressed via depth and surface area is necessary. Table
4 provides an example of how rates are to be expressed (gallons specified per surface area at
specific depths are merely for demonstration purposes and are not part of EPA labeling). The
following labels, and any other labels that allow for aquatic application, may need to update their
label in accordance to this label clarification: 62719-687, 5905-580, 67690-50, 42750-127,
42750-243, 62719-187, 62719-37, 67690-42, 67690-50, 70506-228, 81927-13.
Table 4. Example table of application rates expressed as gallons via depth and surface area
Concentration of Triclopyr Acid in Water (ppm ae)
Water
Depth (ft)
0.75 ppm
1.0 ppm
1.5 ppm
2.0 ppm
2.5 ppm
Gallons of Product per Surface Acre at Specified Depth
1
0.7
0.9
1.4
1.8
2.3
2
1.4
1.8
2.7
3.6
4.6
3
2.1
2.7
4.1
5.4
6.8
4
2.7
3.6
5.4
7.2
9.1
5
3.4
4.5
6.8
9.0
11.3
6
4.1
5.4
8.1
10.9
13.6
7
4.8
6.3
9.5
12.7
15.8
8
5.5
7.2
10.9
14.5
18.1
9
6.1
8.1
12.2
16.3
20.4
10
6.8
9.0
13.6
18.1
22.6
15
10.2
13.6
20.4
27.2
33.9
20
13.6
18.1
27.2
36.2
45.3
B. Tolerance Actions
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The Agency anticipates revising several tolerances for triclopyr to be consistent with updated
commodity definitions and current rounding practices. Please refer to Section III. A 3 for more
details. The Agency will use its FFDCA rulemaking authority to make the anticipated changes to
the tolerances.
C.	Interim Registration Review Decision
In accordance with 40 CFR  155.56 and 155.58, the Agency is issuing this ID. Except for the
Endocrine Disruptor Screening Program (EDSP) and the Endangered Species Act (ESA)
components of this case, the Agency has made the following interim decision: additional data are
required and changes to the affected registrations and their labeling are needed at this time, as
described in Section IV. A and Appendices B and C.
In this ID, the Agency is making no human health or environmental safety findings associated
with the EDSP screening of triclopyr, nor is it making a complete endangered species finding.
Although the Agency is not making a complete endangered species finding at this time, the
mitigation described in this document is expected to reduce the extent of environmental exposure
and may reduce risk to listed species whose range and/or critical habitat co-occur with the use of
triclopyr. The Agency's final registration review decision for triclopyr will be dependent upon
the result of the Agency's ESA assessment and any needed  7 consultation with the Services
and an EDSP FFDCA  408(p) determination.
D.	Data Requirements
A Generic Data Call-In (GDCI-116001-1546) was issued for triclopyr for data needed to conduct
the registration review risk assessments. All data requirements have been satisfied, except for
the following:
	guideline 850.2100 avian acute oral toxicity study with a passerine bird (MRID
50294201 is currently in review)
	non-guideline residues in pollen and nectar/field residue analysis (Tier II)
	non-guideline semi-field testing for pollinators (tunnel or colony feeding, Tier II)
A guideline 870.3465 90-day inhalation toxicity study was also required as part of the triclopyr
registration review GDCI (GDCI-116001-1546). Although this study has not been submitted,
when a respirator requirement is added on labels to protect mixers/loaders for aerial forestry
application via helicopter, the Agency will consider waiving the 90-day inhalation toxicity data
requirement.
The EPA has determined Tier II honey bee data for triclopyr acid and BEE are needed, based on
the results of the Tier 1 data {i.e., laboratory studies) and other lines of evidence. See Section III.
B. 3. Ecological and Environmental Fate Data Needs for additional detail.
Due to the uncertainty regarding triclopyr's ability to persist in compost, the EPA will be
requiring the following compost studies:
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o a modified guideline 835.6100 terrestrial field dissipation study with a duration of at least
30 days,
o a non-guideline compost kinetics study for vegetative material and manure,
o a non-guideline compost bioassay study for both vegetative material and manure.
The Agency intends to issue a data call-in to require these compost studies. If on-field dissipation
study shows that residues dissipate rapidly after application and are not of concern, the compost
kinetics and compost bioassay studies are not needed.
V. NEXT STEPS AND TIMELINE
A.	Interim Registration Review Decision
A Federal Register Notice will announce the availability of this interim decision for triclopyr. A
final decision on the triclopyr registration review case will occur after: (1) an EDSP FFDCA 
408(p) determination and (2) an endangered species determination under the ESA and any
needed  7 consultation with the Services.
B.	Implementation of Mitigation Measures
Once the Interim Registration Review Decision is issued, the triclopyr registrants must submit
amended labels that include the label changes described in Appendices B and C. The revised
labels and requests for amendment of registrations must be submitted to the Agency for review
within 60 days following issuance of the Interim Registration Review Decision.
Registrants must submit a cover letter, a completed Application for Registration (EPA form
8570-1) and electronic copies of the amended product labels. Two copies for each label must be
submitted, a clean copy and an annotated copy with changes. In order for the application to be
processed, registrants must include the following statement on the Application for Registration
(EPA form 8570-1):
"I certify that this amendment satisfies the requirements of the Triclopyr Interim Registration
Review Decision and EPA regulations at 40 CFR Section 152.44, and no other changes have
been made to the labeling of this product. I understand that it is a violation of 18 U.S.C. Section
1001 to willfully make any false statement to EPA. I further understand that if this amendment is
found not to satisfy the requirements of the Triclopyr Interim Registration Review Decision and
40 CFR Section 152.44, this product may be in violation of FIFRA and may be subject to
regulatory and/or enforcement action and penalties under FIFRA."
Within the required timeframe, registrants must submit the required documents to the Re-
evaluation section of EPA's Pesticide Submission Portal (PSP), which can be accessed through
EPA's Central Data Exchange (CDX) using the following link: https://cdx.epa.gov/. Registrants
may instead email or send paper copies of their amended product labels, with an application for a
fast-track, agency-initiated non-PRIA label amendment to Andrew Muench, so long as the labels
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and application are submitted within the required timeframe. Registrants who wish to submit
label amendments via paper copy must contact Andrew Muench at muench.andrew@epa.gov to
make the necessary arrangements.
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Appendix A: Summary of Maximum RQs for Triclopyr by Use Site

A=
=acute RQ; C=chronic RQ; Ar=aerial RQ; Gr=ground RQ


Use site
Mammals
Birds, reptiles,
and terrestrial
phase
amphibians
Terrestrial
invertebrates
Aquatic
Invertebrates
Fish
Terrestrial
plants
Aquatic plants
Rice
A=0.1
C=2.6
A=0.19
C=1.5
n/a
n/a
n/a
Ar=3.5
Gr=0.069
n/a
Turf
A=0.35
A=l.l
A<0.11
A=.03
n/a
Ar=9.3
0.1

C=8.7
C=5
C=23
C=.14

Gr=1.85

Forestry
A=0.99
A=3.1
A<0.16
A=0.13
n/a
Ar=55
0.5

C=25
C=14
C=141
C=0.6

Gr=l 1

Non-crop areas,
A=1.5
A=4.6
A<0.24
A=0.16
n/a
Ar=83
0.6
rights of ways, spot
C=37
C=22
C=211
C=0.6

Gr=17

treatment of







grazable land







intersecting with







non-crop areas







Pasture and
A=0.33
A=1.03
A<0.65
A=0.17
A=0.74
19
0.59
rangeland
C=3.0
C=4.8
C=47
C=0.6
C=0.54


(applications at 2 lb
ae/A rate)







Aquatic weed
n/a
n/a
n/a
A=0.04
A=0.04
n/a
1.2
control



C=6.0
C=1.8


Cut Stump
n/a
n/a
n/a
A=0.4
n/a
n/a
1.4
Treatment



C=1.0



	Terrestrial mammals, birds: Acute LOC=0.5; Chronic LOC=1.0
	Terrestrial Invertebrates: Acute LOC=0.4; Chronic LOC=1.0
	Aquatic Animals: Acute=0.5; Chronic=1.0
	Terrestrial and Aquatic Plants: LOC=1.0
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Appendix B: Summary of Risk Mitigation for Triclopyr
Registration Review Case #: 2710
PC Codes: 116000 116001. 116002. 116004
Chemical Type: Herbicide
Chemical Family: Pyridine carboxylic acid
Mechanism of Action: mimics naturally occurring plant hormones, therebv disrupting growth
Affected Population(s)
Source of Exposure
Route of Exposure
Duration of
Exposure
Potential Risk(s) of Concern
Actions
Mixers/Loaders for
aerial forestry
application via
helicopter
Aerial application
Inhalation
Short- and
inlermcdiate-lcrm
Acute toxicity
Addition of respirator for workers
mixing/loading for aerial forestry application
via helicopter
Terrestrial Plants
Spray Drift and
runoff, residues in
compost
Foliar absorption,
plant uptake
N/A
Growth, bio mass
Enforceable spray drift reduction measures
Instructions for the user not to transport offsile
treated plant material or manure from animals
grazing in treated areas for compost for 30-
dav s after application
Grazing animal clean out period of 3 days
Mammals
Application to crops.
Sprav Drift
Dietary
Acute, chronic
Litter si/.c. offspring weight,
and offspring survival
Enforceable spray drift reduction measures
Birds. Reptiles.
Terrestrial
Amphibians
Application to crops.
Spray Drift
Dietary
Acute, chronic
Offspring survival
Enforceable spray drift reduction measures
Terrestrial Pollinators
Spray Drift
Dietary
Acute, chronic
Adult and offspring survival,
and offspring emergence
Enforceable spray drift reduction measures
Freshwater Fish
Aquatic Application,
runoff
Ingestion.
Dermal absorption
Chronic
Growth. Biomass
Fish and aquatic invertebrate statement
Surface water advisory
Freshwater
Invertebrates
Aquatic Application,
runoff
Ingestion.
Dermal absorption
Chronic
Amount of offspring
Fish and aquatic invertebrate statement
Surface water advisory
Estuarine/Marinc
Invertebrates (Water
Column)
Aquatic application.
Runoff
Ingestion
Dermal.
absorption
Chronic
Biomass
Fish and aquatic invertebrate statement.
Surface water advisory
Aquatic Non-Vascular
Plants
Aquatic Application.
Runoff
Plant Uptake
N/A
Biomass
Aquatic weed control statement
Surface water advisory
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Appendix C: Labeling Changes for Triclopyr Products
Description
l.ahcl Language lor Iriclopv r Products
Placement on
l.ahcl

End Use Products

Site of
Action Group
Number
Note to registrant:
	Include the name of the ACTIVE INGREDIENT in the first column
	Include the word "GROUP" in the second column
	Include the SITE OF ACTION CODE in the third column; for Herbicides this
is SITE OF ACTION
	Include the type of pesticide {i.e., HERBICIDE) in the fourth column.

Front Panel, upper
right quadrant.
All text should be
black, bold face and
all caps on a white
background, except
the mode of action
code, which should
be white, bold face
and all caps on a
black background;
all text and columns
should be
surrounded by a
black rectangle.
[Applies to all products
except those for residential
consumer use.]

Triclopyr
GROUP HERBICIDE

HERBICIDE
RESISTANCE
MANAGEMENT: Weed
Resistance Management
[Applies to all products
except those for residential
consumer use.]
Include resistance management label language for herbicides from PRN 2017-1 and PRN 2017-2
diftDs://www.eDa.gov/Dest!cide-reg!stration/Dest!C!de-reeistratjon-not!ces-veart
Directions for Use,
prior to directions
for specific crops
under the heading
"WEED
RESISTANCE-
MANAGEMENT"
Updated Gloves Statement
Update the gloves statements to be consistent with Chapter 10 of the Label Review Manual. In
particular, remove reference to specific categories in EPA's chemical-resistance category selection chart
and list the appropriate chemical-resistant glove types to use.
In the Personal
Protective
Equipment (PPE)
within the
Precautionary
Statements and
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Description
l.ahcl Language for Triclopj r Products
Placement on
l.ahcl


Agricultural Use
Requirements, if
applicable
Respirator Language for
aerial applications via
helicopter to forestry use
sites
"In addition, for mixers and loaders supporting aerial applications via helicopter to forestry sites must"
[Note to registrant: If your end-use product only requires protection from particulates only (low
volatility), use the following language:]
"Wear a minimum of a NIOSH-approved particulate filtering facepiece respirator with any N*, R or P
filter; OR a NIOSH-approved elastomeric particulate respirator with any N*, R or P filter; OR a NIOSH-
approved powered air purifying respirator with HE filters."
*Drop the "N" option if there is oil in the product's formulation and/or the product is labeled for mixing
with oil-containing products.
[Note to registrant: For respiratory protection from organic vapor and particulates (or aerosols), use the
following language:]
"Wear a minimum of a NIOSH-approved elastomeric half mask respirator with organic vapor (OV)
cartridges and combination N*, R, or P filters; OR a NIOSH-approved gas mask with OV canisters; OR
a NIOSH-approved powered air purifying respirator with OV cartridges and combination HE filters."
[Note to registrant: For products reauirins protection for oreanic vaoor onlv. use the following
language:]
"Wear a minimum of a NIOSH-approved elastomeric half mask respirator with organic vapor (OV)
cartridges; OR a NIOSH-approved full face respirator with OV cartridges; OR a gas mask with OV
canisters; OR a powered air purifying respirator with OV cartridges."
*Drop the "N" option if there is oil in the product's formulation and/or the product is labeled for mixing
with oil-containing products.
Personal Protective
Equipment (PPE)
within the
Precautionary
Statements
Non-target Organism
Advisory
"NON-TARGET ORGANISM ADVISORY: This product is toxic to plants and may adversely impact
the forage and habitat of non-target organisms, including pollinators, in areas adjacent to the treated site.
Protect the forage and habitat of non-target organisms by following label directions intended to minimize
spray drift."
Environmental
Hazards
Fish and Aquatic
Invertebrate Statement
for Triclopyr BEE
Products
"This product is toxic to fish and aquatic invertebrates. Drift and runoff may be hazardous to aquatic
organisms in water adjacent to treated areas."
Environmental
Hazards
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Description
l.ahcl Language for Iriclopv r Products
Placcmcnl on
l.ahcl
Groundwater Advisory
"GROUNDWATER ADVISORY
This chemical has properties and characteristics associated with chemicals detected in groundwater. This
chemical may leach into groundwater if used in areas where soils are permeable, particularly where the
water table is shallow."
Environmental
Hazards
Surface Water Advisory
for products with Non-
Agricultural uses
"This product may impact surface water quality due to runoff of rain water. This is especially true for
poorly draining soils and soils with shallow ground water. This product is classified as having high
potential for reaching surface water via runoff for several weeks after application."
Environmental
Hazards
Surface Water Advisory
for Products with
Agricultural Uses
"This product may impact surface water quality due to runoff of rain water. This is especially true for
poorly draining soils and soils with shallow groundwater. This product is classified as having high
potential for reaching surface water via runoff for several weeks after application.
A level, well-maintained vegetative buffer strip between areas to which this product is applied and
surface water features such as ponds, streams, and springs will reduce the potential loading of triclopyr
from runoff water and sediment. Runoff of this product will be reduced by avoiding applications when
rainfall or irrigation is expected to occur within 48 hours."
Environmental
Hazards
Aquatic Weed Control
Statement for Products
used to Control Aquatic
Vegetation
"Waters treated with this product may be hazardous to aquatic organisms. Treatment of aquatic weeds
can result in oxygen loss from decomposition of dead biomass. This oxygen loss can cause fish and
invertebrate suffocation. To minimize this hazard, do not treat more than '/? of the water body in a single
operation and wait at least 14 days between treatments to avoid depletion of oxygen due to decaying
vegetation (excluding water infrastructure and constructed conveyances such as drainage and irrigation
canals, ditches and pipelines or reservoirs for drinking water). Begin treatment along the shore and
proceed outward in bands to allow fish to move into untreated areas. Consult with the state or local
Agency with primary responsibility for regulating pesticides before applying to public waters to
determine if a permit is required."
Environmental
Hazards
Clarification of
application rates and
minimum retreatment
intervals for non-crop
areas, forestry, turf,
ornamental, rangeland/
pasture, and aquatic
vegetation management
Labels must clearly state the maximum single application rate, the maximum yearly rate, and the
minimum retreatment interval for all uses. Maximum application parameters are as noted below:
Directions for Use

Use site
Maximum single
application rate (lb ae/A)
Maximum yearly
application rate (lb ae/A)
Minimum retreati
interval (days)
Pasture and rangeland
2
2
28
Spot treatment on non-
cropland, rights of way,
and forestry sites that
intersect grazed areas
(e.g., public easements)
8
8
28
Forestry
6
6
28
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Description
l.ahcl Language for Triclopj r Products
Placcmcnl on
l.ahcl


Non-crop areas (including
rights of ways, fencerows,
and similar areas) for
triclopyr TEA
9
9
28




Non-crop areas (including
rights of ways, fencerows,
and similar areas) for
triclopyr BEE
8
8
28




Turf and ornamentals
1
4
28




Foliar applications to
floating/emerged weeds
in aquatic water bodies
6
6
14


Rate clarification for
grazable areas intersecting
with treated non-cropland,
rights of way, and forestry
sites
Replace label language specifying rates for grazable areas intersecting with treated non-cropland, rights
of way, and forestry sites with:
"The maximum application rate for spot treatments on non-cropland, rights-of-way, and forestry sites
that intersect grazed areas is 8 lb ae/A/year."
Directions for Use
Rate clarification for in-
water application for
aquatic weed control use
(acre-foot units, water
depth, and surface area
information)
The rates for aquatic weed control should include the appropriate units associated with these applications
(lb ae of triclopyr/acre-foot) and also reflect the appropriate depth and area of the water body to help add
clarity to the label. A table can be included which provides information on rates expressed via depth and
surface area.
Directions for Use
Compost restriction
Clean out period for
livestock
"This product is persistent and may be present in treated plant materials for over 30 days after
application. Do not sell or transport treated plant materials or manure from animals that have grazed on
treated plant materials off-site for compost distribution or for use as animal bedding/feed for 30 days
after application."
Directions for use
For products with pasture
and turf use sites
"Animals that have been fed triclopyr treated forage must be fed forage free of triclopyr for at least 3
days before movement to an area where manure may be collected, or sensitive crops are grown."


Additional Required
Labelling Action
Applies to all products
delivered via liquid spray
applications
Remove information about volumetric mean diameter from all labels where such information currently
appears.
Directions for Use
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Description
l.ahcl Language for Triclopj r Products
Placemen! on
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Spray Drift Management
Application Restrictions
for all products delivered
via liquid spray and allow
aerial application
"MANDATORY SPRAY DRIFT MANAGEMENT
Aerial ADDlications:
	Do not release spray at a height greater than 10 ft above the ground or vegetative canopy, unless a
greater application height is necessary for pilot safety.
	Applicators are required to select the nozzle and pressure that deliver a medium or coarser droplet
size (ASABE S641).
	If the windspeed is 10 miles per hour or less, applicators must use Vi swath displacement upwind at
the downwind edge of the field. When the windspeed is between 11-15 miles per hour, applicators
must use swath displacement upwind at the downwind edge of the field.
	Do not apply when wind speeds exceed 15 mph at the application site. If the windspeed is greater
than 10 mph, the boom length must be 65% or less of the wingspan for fixed wing aircraft and 75%
or less of the rotor diameter for helicopters. Otherwise, the boom length must be 75% or less of the
wingspan for fixed-wing aircraft and 90% or less of the rotor diameter for helicopters
	Do not apply during temperature inversions."
Directions for Use,
in a box titled
"Mandatory Spray
Drift Management"
under the heading
"Aerial
Applications"
Placement for these
statements should
be in general
directions for use,
before use-specific
directions.
Spray Drift Management
Application Restrictions
for products that are applied
as liquids and allow ground
boom applications
"MANDATORY SPRAY DRIFT MANAGEMENT
Ground Boom ADDlications:
	User must only apply with the release height recommended by the manufacturer, but no more than 4
feet above the ground or crop canopy.
	Applicators are required to select the nozzle and pressure that deliver a medium or coarser droplet
size (ASABE S572).
	Do not apply when wind speeds exceed 15 mph at the application site.
	Do not apply during temperature inversions."
Directions for Use,
in a box titled
"Mandatory Spray
Drift Management"
under the heading
"Ground Boom
Applications"
Spray Drift Management
Application Restrictions
for products that are applied
as liquids and allow boom-
less ground sprayer
applications (this includes
application to roadsides and
rights of ways)
"MANDATORY SPRAY DRIFT MANAGEMENT
Boom-less Ground SDraver ADDlications:
	Do not apply when wind speeds exceed 15 mph at the application site.
	Do not apply during temperature inversions."
Directions for Use,
in a box titled
"Mandatory
Spray Drift
Management"
under the heading
"Boom-less
Applications"
Advisory Spray Drift
Management Language
"SPRAY DRIFT ADVISORIES
THE APPLICATOR IS RESPONSIBLE FOR AVOIDING OFF-SITE SPRAY DRIFT.
Directions for Use,
just below the
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Docket Number EPA-HQ-OPP-2014-0576
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Description
l.ahel Language for Triclopt r Products
Placemen! on
l.ahel
for all products delivered
via liquid spray application
BE AWARE OF NEARBY NON-TARGET SITES AND ENVIRONMENTAL CONDITIONS.
IMPORTANCE OF DROPLET SIZE
An effective way to reduce spray drift is to apply large droplets. Use the largest droplets that provide
target pest control. While applying larger droplets will reduce spray drift, the potential for drift will be
greater if applications are made improperly or under unfavorable environmental conditions.
Controlling Droplet Size - Ground Boom (note to registrants: remove if ground boom is prohibited
on product labels)
	Volume - Increasing the spray volume so that larger droplets are produced will reduce spray drift. Use
the highest practical spray volume for the application. If a greater spray volume is needed, consider
using a nozzle with a higher flow rate.
	Pressure - Use the lowest spray pressure recommended for the nozzle to produce the target spray
volume and droplet size.
	Spray Nozzle - Use a spray nozzle that is designed for the intended application. Consider using nozzles
designed to reduce drift.
Controlling Droplet Size - Aircraft (note to registrants: remove if aerial application is prohibited on
product labels)
	Adjust Nozzles - Follow nozzle manufacturers' recommendations for setting up nozzles. Generally, to
reduce fine droplets, nozzles should be oriented parallel with the airflow in flight.
BOOM HEIGHT - Ground Boom (note to registrants: remove if ground boom is prohibited on
product labels)
For ground equipment, the boom should remain level with the crop and have minimal bounce.
RELEASE HEIGHT - Aircraft (note to registrants: remove if aerial application is prohibited on
product labels)
Higher release heights increase the potential for spray drift.
SHIELDED SPRAYERS
Shielding the boom or individual nozzles can reduce spray drift. Consider using shielded sprayers.
Verify that the shields are not interfering with the uniform deposition of the spray on the target area.
TEMPERATURE AND HUMIDITY
When making applications in hot and dry conditions, use larger droplets to reduce effects of evaporation.
TEMPERATURE INVERSIONS
Spray Drift box,
under the heading
"Spray Drift
Advisories"
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Description
l.ahcl Language lor Iriclopv r Products
Placement on
l.ahcl

Drift potential is high during a temperature inversion. Temperature inversions are characterized by
increasing temperature with altitude and are common on nights with limited cloud cover and light to no
wind. The presence of an inversion can be indicated by ground fog or by the movement of smoke from a
ground source or an aircraft smoke generator. Smoke that layers and moves laterally in a concentrated
cloud (under low wind conditions) indicates an inversion, while smoke that moves upward and rapidly
dissipates indicates good vertical air mixing. Avoid applications during temperature inversions.
WIND
Drift potential generally increases with wind speed. AVOID APPLICATIONS DURING GUSTY
WIND CONDITIONS.
Applicators need to be familiar with local wind patterns and terrain that could affect spray drift."

Advisory Spray Drift
Management Language
for products that are applied
as liquids and allow boom-
less ground sprayer
applications
"SPRAY DRIFT ADVISORIES
Boomless Ground ADDlications:
Setting nozzles at the lowest effective height will help to reduce the potential for spray drift."
Directions for Use,
just below the
Spray Drift box,
under the heading
"Spray Drift
Advisories"
Advisory Spray Drift
Management Language
for all products that allow
liquid applications with
handheld technologies
"SPRAY DRIFT ADVISORIES
Handheld Technology ADDlications:
 Take precautions to minimize spray drift."
Directions for Use,
just below the
Spray Drift box,
under the heading
"Spray Drift
Advisories"
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Docket Number EPA-HQ-OPP-2014-0576
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Appendix D: Endangered Species Assessment
In 2013, the EPA, along with the Fish and Wildlife Service (FWS), the National Marine
Fisheries Service (NMFS), and the United States Department of Agriculture (USDA) released a
summary of their joint Interim Approaches for assessing risks to endangered and threatened
(listed) species from pesticides. These Interim Approaches were developed jointly by the
agencies in response to the National Academy of Sciences' (NAS) recommendations that
discussed specific scientific and technical issues related to the development of pesticide risk
assessments conducted on federally threatened and endangered species.
Since that time, EPA has conducted biological evaluations (BEs) on three pilot chemicals
representing the first nationwide pesticide consultations (final pilot BEs for chlorpyrifos,
malathion, and diazinon were completed in January 2017). These initial pilot consultations were
envisioned to be the start of an iterative process. The agencies are continuing to work to improve
the consultation process. For example, after receiving input from the Services and USDA on
proposed revisions to the pilot interim method and after consideration of public comments
received, EPA released an updated Revised Method for conducting national level BEs in March
2020.24
Also, a provision in the December 2018 Farm Bill included the establishment of a FIFRA
Interagency Working Group to provide recommendations for improving the consultation process
required under section 7 of the Endangered Species Act for pesticide registration and
Registration Review and to increase opportunities for stakeholder input. This group includes
representation from EPA, NMFS, FWS, USDA, and the Council on Environmental Quality
(CEQ). Given this new law and that the first nationwide pesticide consultations were envisioned
as pilots, the agencies are continuing to work collaboratively as consistent with the congressional
intent of this new statutory provision. EPA has been tasked with a lead role in this group, and
EPA hosted the first Principals Working Group meeting on June 6, 2019.
Given that the agencies are continuing to develop and work toward implementation of
approaches to assess the potential risks of pesticides to listed species and their designated critical
habitat, the ecological risk assessment supporting this ID for triclopyr does not contain a
complete ESA analysis that includes effects determinations for specific listed species or
designated critical habitat. Although the EPA has not yet completed effects determinations for
specific species or habitats, for this ID, the EPA's evaluation assumed, for all taxa of non-target
wildlife and plants, that listed species and designated critical habitats may be present in the
vicinity of the application of triclopyr. This will allow the EPA to focus its future evaluations on
the types of species where the potential for effects exists once the scientific methods being
developed by the agencies have been fully vetted. Once that occurs, these methods will be
applied to subsequent analyses for triclopyr as part of completing this registration review.
24 https://www.epa.gov/endangered-species/revised-mefhod-national-level-listed-species-biological-evalnations-
eonventional
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Appendix E: Endocrine Disruptor Screening Program
As required by FIFRA and FFDCA, the EPA reviews numerous studies to assess potential
adverse outcomes from exposure to chemicals. Collectively, these studies include acute, sub-
chronic and chronic toxicity, including assessments of carcinogenicity, neurotoxicity,
developmental, reproductive, and general or systemic toxicity. These studies include endpoints
which may be susceptible to endocrine influence, including effects on endocrine target organ
histopathology, organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates,
reproductive loss, and sex ratios in offspring. For ecological hazard assessments, the EPA
evaluates acute tests and chronic studies that assess growth, developmental and reproductive
effects in different taxonomic groups. As part of its most recent registration decision for
triclopyr, the EPA reviewed these data and selected the most sensitive endpoints for relevant risk
assessment scenarios from the existing hazard database. However, as required by FFDCA 
408(p), triclopyr is subject to the endocrine screening part of the Endocrine Disruptor Screening
Program (EDSP).
The EPA has developed the EDSP to determine whether certain substances (including pesticide
active and other ingredients) may have an effect in humans or wildlife similar to an effect
produced by a "naturally occurring estrogen, or other such endocrine effects as the Administrator
may designate." The EDSP employs a two-tiered approach to making the statutorily required
determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a
chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal
systems. Chemicals that go through Tier 1 screening and are found to have the potential to
interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where the
EPA will determine which, if any, of the Tier 2 tests are necessary based on the available data.
Tier 2 testing is designed to identify any adverse endocrine-related effects caused by the
substance, and establish a dose-response relationship between the dose and the E, A, or T effect.
Under FFDCA  408(p), the Agency must screen all pesticide chemicals. Between October 2009
and February 2010, the EPA issued test orders/data call-ins for the first group of 67 chemicals,
which contains 58 pesticide active ingredients and 9 inert ingredients. The Agency has reviewed
all of the assay data received for the List 1 chemicals and the conclusions of those reviews are
available in the chemical-specific public dockets. A second list of chemicals identified for EDSP
screening was published on June 14, 2013,25 and includes some pesticides scheduled for
Registration Review and chemicals found in water. Neither of these lists should be construed as a
list of known or likely endocrine disruptors. Triclopyr is not on either list. For further
information on the status of the EDSP, the policies and procedures, the lists of chemicals, future
lists, the test guidelines and the Tier 1 screening battery, please visit the EPA website.26
In this ID, the EPA is making no human health or environmental safety findings associated with
the EDSP screening of triclopyr. Before completing this registration review, the Agency will
make an EDSP FFDCA  408(p) determination.
25	See http://www.reaulations.gov/#!documentDetail:D=EPA-HO-OPPT-2009-0477-0Q74 for the final second list of
chemicals.
26	https://www.epa.gov/endocrine-dismption
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